Kant’s critique of Descartes’ theory of knowledge

Adan asked:

What would Kant think about Descartes’ theory of knowledge?

Answer by Geoffrey Klempner

We don’t need to speculate about what Kant would think about Descartes’ theory of knowledge because Kant spells out his disagreement with Descartes in the Critique of Pure Reason.

Descartes believed that it was possible to intuit certain metaphysical truths because we have ‘clear and distinct’ ideas of them. But this is only on the condition, as he acknowledges, that God exists – which he thinks he can prove. If all my experience were produced by an evil demon then no ideas are clear or distinct even if we think they are. If God exists, then provided we use our powers of judgement responsibly, we can rely on our capacity to discover truths about the external world.

Descartes believes that he has a ‘clear and distinct’ idea of his soul qua ‘immaterial substance’. Belief in the existence of body as ‘material substance’ is justified because he experiences bodies outside him, in addition to his own material body, and God is no deceiver.

Kant has responses to all these points. In the ‘Refutation of Idealism’ in the Second Edition of the Critique of Pure Reason, he argues that experience is only possible on the condition that it takes a certain form, viz. spatio-temporal. We would be unable to identify ourselves as a subject if all we experienced was a series of experiences arranged in time.

A lot has been written about this remarkable argument, as an example of what has come to be known as a ‘transcendental argument’. Very good accounts can be found in P.F. Strawson The Bounds of Sense (1966) and C. Peacocke Holistic Explanation (1979).

In the ‘Paralogisms of Transcendental Psychology’ in the second part of the Critique of Pure Reason, Kant argues that knowledge of my identity through time as an immaterial substance is illusory. There would be no way to tell the difference between a continuing ‘soul’ and a series of momentary ‘souls’ communicating their states to one another like a line of colliding pool balls. In his terms, we mistake the ‘a priori unity of apperception’ for the perception of unity. Self-identity is a necessary theoretical parameter in deciphering experience, not something we actually experience.

For Kant, all we have is experience taking a spatio-temporal form, from which we form judgements about objects in space and our own position as an observer relative to those objects.

But now comes the crunch: there is no way to prove the existence of God, as Kant claims in his critique of the Cosmological, Teleological and Ontological arguments. All we can say (some commentators would say this is already saying too much) is that in addition to the world of phenomena, of which we can have knowledge in the ways described, there is a noumenal world, beyond space and time, strictly inconceivable to the human mind. If God exists, then that would be a fact about the noumenal world. Descartes’ claim that reality consists of immaterial and material substance – souls and bodies – goes beyond anything that human beings could ever know.

Verificationism and the self-defeating argument

Millie asked:

Who was it that first pointed out that the verification principle fails to stand up to its own criterion?

Answer by Graham Hackett

One of the most famous statements about verificationism is that it is self defeating under its own terms. A statement can only be verified, (according to verificationism), if it is either an analytic statement (self-evident) or shown to be true by scientific proof. However, we can argue that the statement of the verification principle is neither analytic, nor supported by scientific proof. Therefore it is self defeating. We need to be careful in just baldly stating this as an anti-verificationist argument, since Ayer and Carnap, and other empiricists attempted changes in definition in response to the self-defeating argument. We would need to check whether all definitions have the same weakness. 

In not answering your exact question about the origin of the self-defeating argument (SDA), I find that it it is mentioned many times by critics, but none of them admit to its first formulation. My own view was that it was kicked around by the Vienna school for some time, asserted, refuted and re-asserted. The SDA  may well have even been first formulated by a verificationist! The nearest I can get to a meaningful answer is to suggest that a reading of the argument between Carnap and Putnam would be revealing. But I don’t think that the SDA can be traced to any one source.

As an observation on SDA’s generally, they can be found in other areas of philosophy. For example, the foundationalist argument for knowledge, is (by some accounts) based on the idea that knowledge is based upon arguments, which are themselves based on further arguments, and so on, until we reach an argument which is final and needs no further support. Foundationalism, it is argued, is self defeating because it has no such  basic foundation. SDA’s have sometimes been described as themselves being self–defeating because the argument always regresses to something which cannot be supported by any further evidence, and which has to be held to be true by stipulation. Wittgenstein in his latter days may have held such a view. SDA’s can be very clever, but they are often wearisome.

Rather than rely on the SDA criticism of verificationism, a more powerful criticism is that it is based on a simplistic view of how science is conducted. Scientific procedure is not always based upon proceeding from one set of facts to another set of facts. Sometimes it proceeds by making assumptions or stipulations. Einstein based his success on making the assumption that the speed of light is fixed, and that nothing can exceed it. It has never been proved in the analytic sense, but the assumption has so far yielded correct calculations and forecasts. Quarks, bosons and other particles were long assumed to exist, even though no direct evidence existed for them. (That evidence was found long after this assumption was made.) It is very difficult to see how verificationism could cope with this approach to science. Karl Popper also remarked that his “falsifiable” approach to the conduct of science had killed verificationism. Even if Popper’s blow was not fatal, the description of science contained in Thomas Kuhn’s Structure of Scientific Revolutions was.

Also much more powerful than the SDA, is the serious attack on verificationism made by Quine in his paper “Two Dogmas of Empiricism”. Are there any really self-evident propositions? Further, he questioned the whole notion of truth as consisting of atomistic self-evident or scientifically-proven propositions. Truth was much more a question of a mutually supportive network of propositions.

This argument is not as clever as the SDA, but it is more rewarding.

Asking the Big Questions (2)

Ross asks:

I’m a graduate in philosophy and I wish to write a book in philosophy. The title I have in mind is “Why philosophy matters: Asking the Big Questions”. I’m looking for advice as to whether this is a good theme for a book and what topics I should include in the book. I welcome any advice. Thanks.

Answer from Peter Jones

I feel it is an excellent idea for a book. But are you able to write it? Do you understand philosophy? Do you know why it’s important? Can you answer any of the big questions? The average professor of philosophy cannot answer these questions in the affirmative with the consequence that philosophy departments are facing growing criticism from the rest of the university and scientism is on the rise. It seems unlikely that a recent graduate can do any better than the professors who taught him.

I would suggest holding off on the book until you can answer the big questions. Otherwise it’ll be just another book telling us how the study of philosophy exercises our brain and helps prevent dogmatism but is otherwise useless, and there are plenty of these about already.

But don’t let me put you off. You might write something brilliant. I would start with the question ‘Why is philosophy difficult?’ This meta-question encapsulates all the others. The question ‘Why does philosophy matter?’ is a good one but you’ll have to provide a much better answer than your professors if the book is going to be interesting.

If you check the archives at https://dailynous.com ( a pro bulletin board) you’ll find much discussion of the current crisis in philosophy and the threat of job-losses and department closures, but no solutions. If you can provide one you’ll be the saviour of the hour.

As for topics, the heart of philosophy is metaphysics so a selection of metaphysical questions will do. All metaphysical questions are ‘big’ questions. But why persuade people to ask such questions unless you can answer them? Surely it should be you asking them and searching for answers. I worry this will be another book damning philosophy by discussing lots of important questions and failing to answer any, and there is already a vast literature that takes this approach. For this reason I feel you might be better choosing a more unusual title and theme and finding a new angle.

Don’t let me put you off since a good book is a good book even if it covers old ground. You may write something of great value to your intended audience. But were I a publisher I’d want something more exciting from an unknown author.

This is not advice but just thoughts. If you’re fired up to write then write.

Parts and wholes

Salih asks:

I had an argument with a friend of mine concerning part whole relation, he argues that there cannot be any entity with parts because of a contradiction. Nothing can be many things (so only unities can exist) so for example he says an animal cannot be one for it has diverse parts and so one part say a wing cannot be a hand for it will cease to be a wing and nothing can be many things so nothing can unite these things. So how should I reply?

Answer from Craig Skinner

Ah, you and your friend have started a discussion on mereology (the logic of parts and wholes) and are touching on the special composition question, gerrymandered objects and mereological nihilism.

But I wont go into any of that here. You and your friend will get round to it if you keep going.

How should you reply, you ask.

To keep things going I suggest you tell your friend you wont listen to him because he doesnt exist. He is a (human) animal, having diverse parts, and so, by his own admission, not a unity and therefore non-existent. Ask him, too, why he bothers to argue with you since he knows you dont exist either. It may help your exchange if you agree that, although you dont exist, being just a collection of parts (ultimately fundamental particles) arranged Salih-wise, and he is just particles arranged friend-of-Salih-wise, you can pretend to exist.

It’s hard work, though, pretending to exist when you dont, and so, worn out with it, I’ll settle the Craigwise-arranged particles in my favourite easychairwise particle arrangement, and leave you and your friend to get on with it till you get things clear.

Asking the Big Questions

Ross Campbell asks:

I’m a graduate in philosophy and I wish to write a book in philosophy. The title I have in mind is “Why philosophy matters: Asking the Big Questions”. I’m looking for advice as to whether this is a good theme for a book and what topics I should include in the book. I welcome any advice. Thanks.

Answer from Craig Skinner

I applaud your ambition.

I answer as a potential reader, rather than as a writer. My own writings comprise scientific and medical papers and the occasional book chapter, and more recently, philosophy articles and editorials online. No book.

Your book sounds as if it’s intended for educated general readers. If considering buying your book, I would ask myself if it adds anything to existing titles. So I suggest you read (maybe you have) these 3 recent short books on the same theme:

Ultimate Questions (2016) Bryan Magee

What is philosophy for (2018) Mary Midgeley

What is philosophy and Why Study It? the Case for Relevance (2020) Max Malikow

Proceed if you feel you can add something or do it better.

As for title, it’s OK, a bit ho hum (yawn), Magee and Midgeley are snappier, but at least it tells us the content. Cynics of course will say, these people forever ask the questions, never answer them.

Content will include:

What exists?  matter, the external world, selves, God, free will, numbers, possibilities, causes etc

What can we know? what is knowledge, can we be certain, scepticism, limits (Godel, Heisenberg), logics etc

How should we live? ethics (meta-, systems, practical), philosophy as ways of life etc

Good luck. I hope you get a perspective from those who have written books, especially successful ones.

More on too much philosophy

Saleh asks:

How to stop thinking philosophically about everything? I feel that instead of enjoying life and the things around me I put so much energy and time analyzing them and looking for explanations like thinking in terms of of Aristotle’s causes or in terms of part-whole relations and so many ‘why’ and ‘how’ questions. So how to lose interest in that or at least how to learn not to put so put so much energy and time on it?

Answer by Craig Skinner

Geoffrey Klempner has given a brilliant answer. I agree with all he says.

I just want to add one comment.

One reason people may be put off philosophy is that the subject sometimes seems remote from everyday life. Modern academic philosophy is a specialized, technical field with journal articles opaque to the general reader or even to other philosophers working in different branches of the subject. And  I can understand that the average student might wilt during the seminar on alternatives to material implication as truth conditions for counterfactual conditionals, and head for a fun evening with friends as soon as it’s over.

But philosophy wasnt always a subject for essays, exams and degrees.

How should we live? That was the central question for the ancient greats, with Socrates, Aristotle, Stoics, Epicureans and Neoplatonists (and the greats of Indian and Chinese philosophy) offering different, overlapping views. They all assumed cosmic order within which humanity had a proper place, and the task was to define that place. But this was overtaken in the West by Christianity, which imposed its own vision of how we should live. However, it has resurfaced, especially in Continental philosophy, since the “death of God” but without the assumption of cosmic order, so that the question has become, not how should we live, but how might we live, the central concern of Deleuze, Derrida or Foucault. If there are no constraints due to preordained cosmic order or fixed human nature (I dont say I agree with this), then we can improvise and experiment with ways of living, and not just understand, but change, the world, maybe for the better.

At any rate, philosophy as a way of life is back on the table, whether Socratic, Stoic, Aristotelian, Deleuzian, Nagarjunian or whatever, and Geoffrey and Pathways has done much to promote the idea that philosophy is for everybody and is central to worthwhile human life.