Through the years, we brought two German Shepherd pups into our home, one eight weeks of age, the other ten weeks, and began the delightful and difficult process of acculturating them into our world, teaching them to fit in, to act in ways that seemed best – to us. That’s the key, isn’t it, to get a dog to do what you want, for them to follow the rules you lay down, so that your life is easier, so that they don’t disrupt the life you wish to live, allowing you to enjoy their company while experiencing the minimum amount of hassle from their presence. And of course, this is best for them too – isn’t it?

Dante was a sable male, the epitome of a trustworthy and loyal friend. He almost always did what he was supposed to do, seemed to take great delight in doing what we had defined as the right thing, even if it went against his natural instincts. He had a fierce commitment to fulfilling his duties. Was this rational behavior?

Shakti was a black and tan female who learned fast, learned to fit in and follow the rules – and gradually learned to get what she wanted within those rules. She became quite good at it; at times we wondered who was managing whom in the household. She would act like she wanted to be petted in order to get our attention, then promptly switch and demand a treat – the petting being a tactic to get something else, the treat. I wonder if Shakti was rational.

Reason and rational have been used to describe something that lies at the very heart of what it means to be human.² And as Shakespeare suggests, they constitute the primary basis upon which we assign ourselves a more evolved state than that of all other creatures. Yet the use of these words is highly problematic, for they mean quite different things to different people, and often even to the same person at different times.

I know, I know, some people think that dogs are not “rational.” But that is the human point of view. Sometimes I wonder if dogs think humans are rational. Rather than arguing about this, however, and instead of slipping and sliding around in our minds between several different understandings and definitions as we usually do, let’s consider more carefully just what “reason” and “rational” mean. Perhaps we can sort out some of the confusion surrounding these words, and render them a bit more useful in dealing with our life issues and decisions.

While we’re at it, let us also note that great confusion exists in our conversations with others when we use these words, each of us blithely using definitions that have little correspondence with the other’s, causing great misunderstanding. Truth be told, most of us have such a loose grip on these words that we shift between meanings all the time, without even recognizing that we are doing so. Yet many people hold that these traits represent the best and primary tool for discovering how to live a full and complete life.

Here then are four of the most important ways these words have been used to define our relationship to values and meanings:

Four Distinct Views of Being Rational

1) Grasping the deepest truths
When Plato focused on reason as the greatest pillar of human understanding, he meant that by discussing, considering, and reflecting upon the important issues of life, we could come to a clear understanding of what was ultimately true. Plato’s idea of truth, however, was grounded in the belief that there was something transcendent to the everyday world – the world of Pure Forms. Plato’s truth was not based on the evidence of our senses, or on an experience of the material world, for he realized that the senses can be deceiving. Rather, through discourse and reflection, reason would lead to an intuitive insight into the true nature of reality, beyond the material realm. In essence, we could come to know the deepest truths by use of a human faculty called reason, but that faculty was not separate from intuition, but operated in full and complete harmony with it. Further, there was no conflict between reason and the spiritual domain – in fact, the knowledge that reason most sought to discover was knowledge of the world of Pure Ideas, or Pure Form – the transcendent realm.

2) Recognizing the importance of duty
Some Rationalists, beginning in the 17th century and exploding into modern thought with the work of Immanuel Kant, tried to establish a basis for human action without reference to Plato’s World of Pure Forms, or any established religious tradition. Kant’s use of “rational” evolved to mean that rather than rush to act on one’s whims, being rational was the ability to stop and consider the consequences of one’s actions in relation to a higher good, the “moral imperative” he formulated. A rational being was one who considered longer term goals and values such as the kind of person one wanted to be, how one’s actions would affect others, and the importance of one’s role in relation to the human community.

Kant’s rationality did not preclude the spiritual realm – in fact, it made explicit room for its existence – but he based his guidance for human action on the cultural values he had inherited. However, Kant did not fully deal with the fact that the cultural teachings in which he was embedded arose from a spiritual tradition. He seemed to think he had made a rational argument for their truth, but that argument is not persuasive to most people today. He also struggled with, but did not adequately deal with the fact that his core assumptions – which did not arise from reason – basically came down to his belief that his culture’s values and meanings were “The Truth.” It is therefore fascinating to note that in giving duty the highest role in moral guidance, he is following in the footsteps of the ancient Upanishads of India: fascinating because, although both give a central role to duty, how that duty is defined is quite different. (It is highly unlikely that Kant knew the teachings of the Upanishads.)

For Kant, reason offered compelling justification for the duties and responsibilities that his culture defined as right and good. Based on these values, he argued that to give in to one’s whims and passions was not rational, whereas doing one’s duty within the culture was a supremely rational path. This understanding of rational is still very much operative for many people today.

3) Freeing ourselves from blind obedience to authority
In the 18th century, the earlier ideas of Spinoza and Leibniz inspired many thinkers such as Voltaire and Thomas Jefferson to view reason as the primary tool to be used in making the important decisions of life. Although also indebted to Kant, their goal was quite different from his, in that they wished to jar people from a blind obedience to authority, and to break them free from some aspects of their cultural heritage. Their rationalism meant that, rather than follow the rules and injunctions of one’s church or culture, one would use reason to discover for oneself the right way to live. A rational being would stop, reflect, and think through issues, would listen to the arguments of others, consider all the evidence that was available, and then come to a personal independent judgment as to what seemed right and true.

This branch of rationalism did not preclude the use of intuition, nor did it preclude the existence of the spiritual domain. It simply refused to accept the right of any established church or political authority to interpret the spiritual realm for the individual. A good example of this is Voltaire. Although often viewed by history as an atheist, such was not the case. For him, the existence of something spiritual, an unseen presence, was the conclusion to which reason itself led: “It is perfectly evident to my mind that there exists a necessary, eternal, supreme, and intelligent being. This is no matter of faith, but of reason.” ³

This group of thinkers, then, who strongly affected the American Revolution, championed reason, but not in opposition to intuition or the spiritual dimension of life. Most were Deists, who believed that God had set the world in motion, and that reason itself was the greatest gift which this Creator had bestowed on humankind. Once again, this stream of thought is still very much with us today.

4) Being rational means to be logical
Finally, some thinkers in the late 19th and early 20th Century came to equate the idea of being “rational’ with the idea that truth needed to be demonstrated by logic. Mathematicians had become highly successful in solving a broad range of problems by this time, and it was hoped that all of life could be made subject to the hard logic that prevailed in math. This led to logical empiricism, which in its simplest form held that truth had to be demonstrable to a thinking person’s satisfaction to be true by a logical proof, and if it wasn’t, then it was not true.

This approach is useful in math and science, and for a narrow range of things in daily life – things that can be put into simple categories, such as: Would you rather receive fifty dollars versus one hundred dollars for the jacket you are selling? It is both “logical” and “rational” to choose the one hundred dollars – and this can be presented persuasively to most disinterested observers. But few things in life are this simple, and this kind of 1 + 1 = 2 situation does not exist for many questions we have to deal with in our lives. When things – like love, honor, courage, and meaning – cannot be couched in such simple terms, that which is rational and that which is logical often part ways, sometimes dramatically.

Yet the conflating of logical and rational goes on, becoming a modern habit, causing much mischief. In its defense, some logical empiricists might have thought that by accepting as true only things that were “logical,” they would be able to create a worldview that could be conclusively proved to all. But such has not been the case, and in all likelihood never will be (as we shall consider in the next chapter). The reverse has been the case in modern philosophy: logical empiricism, being shown to be fatally flawed, has been largely abandoned.

Its influence, however, lingers in the modern mind, aided and abetted by those who would like to believe that their worldview is logical, that their assumptions are supported by some kind of unassailable “proof.” This has culminated in a fairly common “street version” of the word rational which suggests that being rational means having logical proof for a view or position. (Amusingly, if someone is challenged to show the proof for something they are asserting to be “rational,” that person, if their core assumptions are questioned deeply enough, falls back ever and always on a claim of authority: it is true because I say so, or because some important person I know says it is true. In pursuing this kind of questioning many times, of myself and others, I have yet to discover a remotely plausible “proof” for a particular worldview, or even for answers to many simple questions we face each day in the living of our lives.)

Belief in the Five Senses

Another stream of thought, British Empiricism, arose in opposition to rationalism. In its simplest form, empiricism is a theory which holds that all we know or can know must be based on an experience of our senses – sight, sound, touch, taste, or smell. This theory began its modern Western journey with the English scholar John Locke, who taught that each child was born as a “blank slate” upon which experience would write all that would ever be known. (However, Locke was not a strict empiricist in the modern sense, for he believed that knowledge of God’s existence, which he affirmed, was gained through intuition rather than through the senses.)

Empiricism has a power all its own, for the truths that arrive through our senses seem so immediate and real (the pain of a needle, the taste of food when hungry, the immediacy of a rock hurtling toward one’s head, the exquisite pleasure of a passionate embrace). We move through the day reliant upon our senses, and in this reliance, it is a small step to begin to mistrust the abstract thoughts and theories parading through our heads. At times, we might fondly wish to be able to organize around solid, tangible things like the hard evidence of our senses, rather than grappling with ephemeral things like emotions, values, belief systems, and meanings.

Empiricism gradually migrated from philosophy to science, and became a central pillar of the magnificent scientific edifice, there yielding the scientific method, the view that all scientific theories must be testable by physical observation of the material world before they can be accepted as true. Since the primary mission of modern science is to examine and understand the material world, this method became profoundly important to its success.

In this arena, empiricism became an ally rather than an opponent of rationalism. But a very limited and specific definition of rationalism – rational equals logical. As allies on the scientific team, these two new friends revolutionized the way we see and understand the material world, creating hard data and testable knowledge that built much of the material world we know today. Magnifique!

Yet as is often the case, success begets … problems. And so it was when this simplified union of empiricism and rationalism migrated back to philosophy, and began to be applied to things beyond the realm of science. If these two currents were to be unified in dealing with questions broader than the scientific, something had to sacrificed, for there were good reasons these two streams had been in conflict. The sacrifice demanded? That everyone give up all other ways of defining and using reason. Out the door was the rationalism of Leibnitz and Kant, the Idealism of Plato and Hegel, the Romanticism of Goethe and Wordsworth, the Transcendentalism of Emerson and Thoreau, and all the ideas proposed within spiritual and religious ways of thinking. Although most everyone through the ages had concluded that beliefs, values, emotions, and ideas about the meaning of life were not based solely upon input of the five senses, were not primarily empirical, under this new banner such views had to be jettisoned and replaced by the single idea that reason and the rational would be confined to sense data and logic. Thus a new worldview was born, which I have come to think of as Pure Materialism (capitalized to capture its essence as a faith system).

The Coming of Pure Materialism

The myth of Pure Materialism begins: Once upon a time a world came to be that was made up only of matter. This world is the world you live in, my child, and here only things that can be measured by instruments are “real,” and only events that can be duplicated in the laboratory are “true.” When this myth is joined with the assertion that if something is “rational,” then somewhere, somehow, there are logical, factual, arguments that prove it – the result is Pure Materialism.

I dwell upon this because so many people I know seem to trip over the idea that to be a good, modern, rational being, one must reject anything that cannot be demonstrated by the evidence of our senses, reject everything for which there is no logical proof. What they do not seem to recognize is that Pure Materialism is not supported by our senses, nor is it supported by any logical proof. It even runs counter to what has been considered rational for most of human history. Pure Materialism is based upon a set of assumptions that are strictly metaphysical, and only if one accepts these assumptions through an act of faith do its conclusions follow.

Yet it is quite easy in the modern world to go down the blind, dark alley of a narrow definition of “rational,” passing unnoticed the most important things in life. To make my assertion as strong as possible: there is not one piece of evidence that Pure Materialism is true. Not one! And it is not the least bit rational, in the way that most human beings have understood that word. There is no evidence whatsoever that something beyond the material does not exist. There are metaphysical theories which hold that nothing but the material exists, but they are not scientific, nor logical, nor demonstrated by the facts. They are speculative, metaphysical theories. One can just as easily assume that consciousness gave rise to the material realm; or that guiding principles exist beyond the material; or that human life has a tendency to move in a meaningful direction; or that a creative force was present at some point in the past, or is present today.

Each of these statements is a metaphysical theory – attempting to explain the ultimate nature of existence. Just as the claim that matter is the measure of all things is a metaphysical theory, so too are each of these. A rational being, by any definition that makes sense, can accept one of them, accept several, or reject them all. Where one stands in this regard has nothing to do with being rational. Wise, thoughtful people have accepted each one of these theories and accept them today. Each has arguments in its favor. Being rational, if it means anything, means being able to consider with all one’s faculties which metaphysical view seems the most “right” in some broad way, for there are no logical proofs out there which demonstrate one to be true and another false.

This is necessarily the case, because the very nature of a metaphysical theory is that it goes beyond the facts, must go beyond the facts. And it goes beyond reason. You see, hard as we might try, we cannot escape the fact that metaphysical theories provide the framework within which “facts” make sense and reason in exercised. It is the sea within which we, as thinking beings, swim. Every set of facts, and the reasoning process itself, has to function within a context that gives definition and meaning to how one will begin the process of reasoning, and of understanding “facts.” The Australian aborigine and the TV climatologist might be equally good at predicting the weather, but their facts and their reasoning will be quite different. The facts and the reasoning of physics make sense within the framework of physics, but that framework is not very helpful in understanding poetry, or romance.

All of this is important because in many arguments about beliefs today, a trump card thrown upon the table is the cry “you are not being rational,” or “reason demands.” But this supposed trump card is actually a bluff, a raw assertion that the player trying to use it owns truth and reason. When played in the metaphysical arena by a Pure Materialist, the contention seems to be that only a Materialist worldview is “rational”– with no recognition that this assertion is based on an act of faith in favor of the Materialist myth about the nature of reality.

Once it becomes clear that all such assertions start with an act of faith, then the recognition dawns that Materialists are simply asserting that everyone should accept their myth as the one true myth, and that we should base our lives upon their particular act of faith about the nature of reality. There is no rationality here, nor reason – simply unproven metaphysical assertion.

William James to the Rescue

Woven through the history of the words “reason” and “rational” is the clear theme that what these words mean for most of us is not in conflict with intuition, nor with spiritual beliefs. On the contrary, from Plato to Einstein, and embracing countless philosophers and scientists including Kant, Locke, Heidegger, William James, Alfred North Whitehead, Descartes, Newton, Jefferson, Voltaire, and so many others it is impossible to recount them, there is no conflict between reason and intuition, nor between rationality and holding spiritual beliefs. On the contrary, reason, rationality, intuition, and spiritual beliefs have been integrated in the worldviews of most great thinkers.

William James, as usual, had a brilliant insight as to how these currents – empiricism, intuition, and spirituality – could be reconciled in light of the modern ascendance of empiricism, helping to found the school of thought known today as Radical Empiricism. The gist of his thinking is this: The experience of our five senses is clearly the basis for much of our knowledge of the world. In the practical functioning of our lives, everything points to the assumption that there is material stuff out there to be dealt with, and that that stuff has a crucial role to play, so let’s not get caught up in discussions about whether we might be a “brain in a jar,” as postulated in one of Descartes’ thought experiments.⁴ In living our lives, said James, we can and should interact with the material world as we experience it, and not worry too much about how our perceptions might be an illusion. To this point, he is with the materialists.

But then a parting of ways: James saw that there are many experiences besides those of our five senses. Emotions, intuitions, and spiritual moments are experiences, and in fact make up a major part of our life experience. They are different from the experience of our five senses, but that does not mean they are any less of an experience. Thus, if we are to be true empiricists (basing our knowledge on experience), we must take all of our experiences into account, including other ways of knowing beyond the five senses.

His message in essence is: in dealing with the material world, let’s do what works. But what works there cannot explain or prepare us for dealing with other areas, such as the emotional, intuitive, or the spiritual. To be truly empirical would be to use the most relevant experience in each arena – and emotions, intuitions, and spiritual experiences are the most relevant data in many areas of life. There is no reason to narrow our possibilities by holding that this data is unempirical, for it arises as a direct experience, provides information that works, and is subject to observation and study. Thus if we are to be truly empirical, we will accept all of our experience as valid and useful, not just that of our five sense.

In this light, James the empiricist could write:

Being Presumptuous – An Attempt at Clarity

I have been pondering the meaning of reason and rationality for the better part of my adult life. If they do not rest solely upon sense data and logic, what do these words mean? As I have reflected on this question, read the views of scholars through the centuries, and surveyed my bemused friends, I have come to see ever more clearly just how much confusion resides here. These words have meant very different things to different people at different times in history, yet each of these meanings still has some purchase today – mingling and overlapping with each other into a crazy quilt of conflicting and incompatible views. Observing this, there is some humor in the recognition that so much confusion and misunderstanding revolves around words that are supposed to establish the very basis for the clarity of human thought.

So let me venture into this jungle with an attempt to clarify, at least for myself, the way in which reason and rationality truly do represent something at the heart of what it means to be human, and what it means to live a thoughtful and examined life.

Here are the ways that reason and rationality add value to my life:

A) Reviewing my whims: Rather than following every whim that arises, being rational means to step back for a moment and consider the consequences of my actions, to take a broader perspective than the urge of the moment. It is to refuse to be a slave to unconscious desires, choosing rather (at least at times) to pursue only those urges and desires that fit the broader goals and visions of my life. It is to use the broadest understanding I can muster to consider how my actions and decisions will fit into the whole cloth of the life I am weaving.

B) Considering all the information available from all possible sources: Reason and rationality suggest the importance of gathering as much information as possible in relation to my significant life decisions, and a willingness to look at all this information in a reflective way with both heart and head. This means being willing to weigh and consider everything: certainly logical arguments and sense data, but also values, beliefs, intuitions, images of the kind of person I wish to be, how the situation affects others, the cultural norms within which I am living – everything. All this being considered, being rational is the attempt to find an overall feeling of “rightness” as to how I will now proceed in my life.

C) Finding a healthy relationship to authority: Using reason is to recognize with the British philosopher Edmund Burke that traditions that have withstood the test of time deserve loyalty and respect. But perhaps more than Burke would have done, to ask of authority: How do you fit with my personal beliefs and values? Do you still serve the highest good, or has time passed you by? Have you been taken over by those who are now using you for their own narrow purposes and ends? Since reason is not limited to or contained within authority, it provides a way to evaluate authority’s effectiveness, and to determine its proper place in my life and in my community’s life. This means that I will not follow authority blindly, whether religious, political, or cultural – reserving the right to question authority, to subject it to scrutiny, to examine its assertions to see if they hold up to the knowledge and understanding of this time and place. Yet always remembering there is an important “reason” to respect authority and tradition.

D) Balancing Autonomy and Community: There is a constant tension between the urge for freedom, independence, personal power, and autonomy on the one hand, and the need to be part of community on the other. In this tug-of-war, reason and rationality are essential tools in discovering the best possible balance between these opposing poles. (Chapter 20)

E) Finding harmony with intuition: For me, reason is in no way opposed to intuition. On the contrary, they are the two legs upon which we walk toward wisdom: if one is missing, the walking is made much more difficult. (Chapter 8).

F) Recognizing the connection with things of the spirit: And for me, reason and rationality in no way conflict with things of the spirit. In fact, through most of human history, although reason and empiricism have often been at odds, reason and things of the spirit have usually been of mutual benefit and support. (See several of the following chapters.)

Perhaps an analogy is in order. Imagine that you are part of a group that has decided to climb Mount Everest. Reason as defined above will play an incredibly important role. However, the motivation to climb Everest is certainly not rational, but falls much more easily into the category of whim. (Whim at its serious and important level, the realm of deep urges and desires that provide the motivational fuel for our living, yet arise from a mysterious place that we really do not understand.)

Truth be told, few of the core motivating forces of our lives are rational. However, reason can be a great aid in sorting through these myriad urges we feel, helping us to decide which might lead to the kind of person we wish to be, and which have some possibility of accomplishment. Further, reason is crucial in determining how they might be accomplished, and in organizing an effective strategy to move toward the ones we have chosen to pursue.

So here we are, being moved for “who knows what reason” to climb Mount Everest, and we realize the next step is to join with a group of others (no one has ever climbed Everest alone) who share our mad vision of enduring enormous pain and hardship to climb the world’s highest mountain simply “because it is there.” Reason plays a role in assembling the group (who is a good climber, who has been before, etc.), but once the group is assembled, rational thinking kicks in ever more strongly in performing its indispensible role: the practical preparation for the climb. Who but reason could calculate the provisions we will need, decide on and coordinate the schedule, assemble maps, collect the reports of previous climbers, research the most useful gear, assign roles of authority within the group, and on and on.

All has gone smoothly, and the climb begins. Roles have been assigned, and we mostly accept our roles, deferring in most cases to the authority structure we have put in place (the guides decide how to respond to the weather, the climb leader decides about changes in route, the medical person decides what to do about illness or injury, etc.). Yet at times, if one of the those in charge seems to be making a mistake, the rest of us might ask them why, question their decision, offer arguments for an alternate path. In short, we will use reason and intuition to question and influence authority. Yet in order to remain a part of the group and to fulfill the common goal, we will often decide to relinquish our individual “reason” and accept the decisions of those who have the leadership roles. Reason here inclines us to accept authority in order to accomplish a common goal. This is reason operating as duty, or more broadly, as the belief that we are so deeply embedded with others that the most rational path is to bend, or even go against, our own views and opinions in order to live a shared life.

Yet we do not always do this. Occasionally we decide that the one in authority is mad, or evil, or cruel, or is about to get us all killed, and we organize a rebellion against authority. In our hypothetical example, let’s say the climb leader, with wildness in his eyes, proclaims that we will make the final assent on the morrow, although everyone can see that a storm is brewing. So we talk to each other conspiritorially, saying the climb leader is affected by the thin air, is old and knows this is his last climb, knows that our provisions are short and if we don’t go tomorrow we will not reach the summit on this trip. We prepare our arguments to each other and ourselves almost as meticulously as did Thomas Jefferson in justifying the rebellion of the colonies against King George. Here, reason is being used to override authority, bringing into stark relief the fact that being rational is not a fixed set of rules, but a broad “feel” for how to proceed.

And speaking of reason as a broad “feel” brings us to the marriage of reason and intuition. Any mountain climber will tell you there are moments when reason gives way to intuition – the best route to take, when to give in to the weather, where to place the hand at a precarious moment, what to do in a sudden life-threatening emergency. Reading the accounts of mountain-climbers, I have been struck by how intuition is the constant handmaiden, consort, and occasional dominant partner with reason. In such an extreme undertaking, as with a successful life, the two cannot be separated.

One more piece of the analogy: In the highest reaches of mountain-climbing, or any extreme adventure, it is amazing how often the spiritual dimension of life is the motivating force, or the sudden guest at the banquet. In Maria Coffey’s Explorers of the Infinite: The Secret Spiritual Lives of Extreme Athletes, case after case is documented in which spiritual experiences spring unbidden from extreme physical circumstances. Further, in interviews with these extreme athletes concerning why they undertook their adventures in the first place, the motivations that emerge often could best be described as spiritual.

All of the above factors, then, are for me a part of what it means to live a rational life: to refuse to be enslaved by whim, by authority, by cultural edit, or even by a narrow definition of reason itself; to gather as much information as possible about the important aspects of one’s life; to reflect fully and truthfully with heart as well as mind upon all the assembled information and wisdom before a decision is made; to consider the effects of one’s actions on friends, family, and community, seeking a balance of “rightness” between one’s own needs and desires and those of others; to remember that, as fallible human beings, we could be wrong (having been wrong many times before), so staying open to ever deeper glimpses into the right path to travel; and to recognize and respect the vital role that intuition and the spiritual play in a successful human life. To return to our analogy, it is holding all the currents involved in a mountain climb in one’s heart and mind simultaneously, with actions and decisions flowing from the consciousness that arises when one is in this place. This is the ideal, seldom reached by mountain-climbers or we normal folk, but this is the “reason” of which Shakespeare could speak so grandly, and the rationality that is worth much time and effort to seek.

As for Shakti and Dante, although I loved them dearly, and found them extraordinarily intelligent beings, I guess I would say that in the above sense, they were not rational. However, one day it struck me quite forcefully – I was trying to teach Shakti a new trick, and I was a bit frustrated because she didn’t understand the word I was using – that she understood almost 50 words of the English language, and I did not understand one single word of hers (although I had come to understand a number of her “looks”). So although she might not fit my definition of rational, the jury is still out as to which of us was smarter.

1 First Folio Edition of Shakespeare’s works. Other additions punctuate this quite differently. Although Hamlet spoke these lines to create a contrast to how he felt in the play, it must have been the predominant view that the audience would have held, against which therefore Shakespeare could contrast Hamlet's mood.

2 Reason and rational will be used here as having virtually identical meanings, the slight difference being that reason is a noun, and rational an adjective. However, as will be made clear, they are both quite different from logic and logical.

3 Voltaire. W. Dugdale, A Philosophical Dictionary ver 2, 1843, Page 473 sec 1

4 Neither James nor Descartes used this exact phrase, “brain in a jar,” but it is the shorthand often used to convey what they were both talking about.

5 William James, Varieties of Religious Experience, p. 388