Is there any clue as to whether there are things that cannot be thought or expressed in thought?

Question

Is there any clue as to whether there are things that cannot be thought or expressed in thought? Everything that can be thought may exist, but are there things that maybe we can't possibly express in words, thought or we can't comprehend or think about. What sorts of philosophical arguments support or reject this idea?

Answer 1

Short Answer

A word like 'thought' is so broad that it is almost meaningless in a philosophical discussion until it is defined, and philosophy is often conceived of as the art of defining words. Traditions in the West tend to have strongly materialist notions of thought, that it is 'emergent' from matter, though there are exceptions, like George Berkeley. Depending on one's theories of mind, thought, and expression, there are various answers. For instance, one can express 'hungry', but is one really expressing the experience of hunger? Alfred Korzybski would argue no.

A map is not the territory it represents, but, if correct, it has a similar structure to the territory, which accounts for its usefulness.
— Alfred Korzybski, Science and Sanity, p. 58.4

It is a useful fiction to equate words and thoughts, but there are many traditions that do not, and Ludwig Wittgenstein doesn't speak for them. So in some traditions, like theology, there are thoughts, such as the thoughts of Yaweh, that cannot be expressed. This also heavily relies on your biases of ontological commitment. What does it even mean for a thought to exist?

Is there any clue as to whether there are things that cannot be thought or expressed in thought?

It depends on what you mean by 'thoughts', 'expression', and the 'existence of things' which are objects of study broadly in the philosophy of mind, the philosophy of language, and ontology.

Long Answer

Which Theory of Thought?

To answer your question, you have to provide some inkling of what 'thought' is. That is to say, there are philosophical theories of thought. One popular group of theories regarding thought are theories of thought that see thought as association (SEP).

Associationism is one of the oldest, and, in some form or another, most widely held theories of thought. Associationism has been the engine behind empiricism for centuries, from the British Empiricists through the Behaviorists and modern day Connectionists. Nevertheless, “associationism” does not refer to one particular theory of cognition per se, but rather a constellation of related though separable theses. What ties these theses together is a commitment to a certain arationality of thought: a creature’s mental states are associated because of some facts about its causal history, and having these mental states associated entails that bringing one of a pair of associates to mind will, ceteris paribus, ensure that the other also becomes activated.

These empirical notions of thought are heavily championed by modern-day cognitive scientists who rely on the fields of neurology and psychology to characterize 'thinking' and 'thought'. So, if one accepts these more materialist notions of thinking, then there are many things that can't be the object of thinking, for instance, one cannot think of the entire number of Pi because it is infinitely long, and no human can have a thought that is infinitely long since humans themselves are not infinite. We can think about the symbol from the Greek alphabet, and we can think about the various methods we use to approximate Pi, but we simply can never calculate Pi in our minds completely because it extends forever.

Continental Traditions

Of course, other philosophers have different notions of 'thought' such as Martin Heidegger who defined thought differently. In What Is Called Thinking? in the opening pages of the book, Heidegger says:

Philosophers are the thinkers par excellence. They are called thinkers precisely because thinking properly takes place in philosophy.

Here 'thought' is restricted to Heidigger to something more profound and elevated than what most refer to as thinking. Shortly after he declares:

Most thought-provoking in our thought-provoking time is that we are still not thinking.

This of course is an indictment of those who do not participate in what might be called critical thinking. If one assumes that 'thought' is the stuff of philosophical discourse only and requires methods such as phenomenological reduction to stop knowing and start thinking, then what can and cannot be thought changes. (Please note that the redefinition of ordinary language for metaphysical usage might be confusing. Ordinary language philosophy picks a bone with this repurposing that sometimes causes confusion.)

Language and Thought

While these 'language games' might drive those who are trapped being literal in their interpretation of language into abject annoyance, from a philosophy of language perspective, they are fair game. In these alternative definitions of thought, philosophers might reject anything they want presuming how they define 'thought'. Can anyone think the thoughts of another person? Most analytical philosophers would concede thoughts themselves are private. In fact, the intersection of language and thought has a dichotomy called the private/public dichotomy that leads to philosophical and linguistic questions of translatability. The Sapir-Whorf hypothesis might be interpreted in an extreme form as claiming that speakers of different languages cannot necessarily think thoughts of others in other languages. Can you accurately philosophize about Gemütlichkeit if all you have is a "rough approximation" of the meaning of the word? Are meanings even translatable? Depends on your views on semantics.

Gods and Godheads

When theology enters, one might be asked 'Can anyone think all the thoughts of God?' I believed the received answer in the Christian tradition is no. There are limits to the thought that a human is encumbered by that God is not. On the other side of the coin, mystics like whirling dervishes work very hard to think the thoughts of God, and in some religious tradition, becoming part of the godhead disagree. A theologian might ask if there are limits to the thoughts God can have. If God is all-powerful, can he bring into existence a thought he himself cannot think?

Koans and Metaphors and the Far East

Have you considered the art of koan? Here, a cultural practice has evolved about devising questions about things that simply cannot be thought. 'What is the sound of one hand clapping?' can be pondered, but can one have a thought that is a correct answer? If someone claims that they have thought about the sound of one hand clapping, are they claiming they have thought about the auditory experience of what is referenced? Do thoughts even encompass memories of auditory experience? Depends on the tradition. In the West, where no-nonsense substance-derived philosophy is the norm, where dialetheisms are avoided or rejected outright, this might be considered Unsinn or nonsense; but in Buddhism and mystical traditions, there are very different notions of thought and what can and cannot be thought.

Summary

Are that thoughts that cannot be thought or expressed? That depends heavily on your metaphysical presumptions. I think it's safe to say that anyone who is confident in their knowledge of being right and wrong doesn't quite understand how philosophy works. But then, that reflects my bias in favor of skepticism and fallibilism, a thought that CAN be thought expressed frequently (by me anyway).

Answer 2

What cannot be thought cannot be thought, and that's it. However, it seems clear that there are things which cannot be thought. How come? The fallacy here is to confuse thought and thing. Thoughts are abstractions and are not therefore identical with the things we think. There is no difficulty thinking about things, including things that cannot be thought, and this simply by thinking about the very idea that there are things that cannot be thought, just as we can talk about things that do not even exist, and even make sentences with subjects of which we only want to say that they do not exist, which in effect says that there are things that do not exist. Neat trick, which reveals itself once we recognise that we never actually think the things themselves, we only think thoughts, and we think thoughts we understand as standing for things. Make believe through and through, but this is all we need to live our lives very effectively.

So there are no things that we (literally) think except the thoughts themselves. So, in effect, every existing thing, save our own thoughts, cannot be thought, while at the same time there is no theoretical limit to what we can think about, including things that do not even exist.