Critically discuss Hume’s views about the rationality of our belief in a mind-independent external world. Is there no way of formulating such a belief in a way that resists sceptical doubts?

In this essay I will outline Hume’s views about the rationality of our belief in a mind independent world and provide criticism from other philosophers as well as my own arguments immediately after the outlining of a Humean theory.

Hume’s epistemological views are that of a skeptic. He concludes that if we are to know anything about the world it has to come from experience, but how does he reach this conclusion?

Relations of Ideas and Matters of Fact.

Hume divides knowledge into two types. Relations of ideas and matters of fact. Propositions using relations of ideas are analytic can be known a priori, without experience of the world apart from the learning of the meaning of the terms. For example, the proposition ‘all unmarried men are bachelors’ is something Hume claims we know to be true simply by understanding the definitions of the words in the sentence.

Importantly Hume points out that relations of ideas do not assert existence. If all men were married, perhaps due to a massive population decrease, the proposition ‘all unmarried men are bachelors’ would not be true and so would not be knowledge. The truth of the statement cannot be ascertained without experience of the world.

Perhaps this can be more clearly illustrated with the inverse example, ‘all unicorns have one horn’. Unicorns are obviously imaginary creatures but the very syllables that make up their name refer to the ‘one horn’. This proposition is not true because the subject does not exist. In this way we can see that a priori knowledge only sheds light on the internal world. I could invent a brand new fictional creature and make up a rule regarding its attributes but it would not be knowledge about that creature because the imagination uses impressions of reality combined together in a way that does not (yet) represent the mind-independent external world (

Hume’s empiricist thesis states that all simple ideas are copies of impressions and that complex ideas can be generated by combination ( A Unicorn is one such creature. Relations of ideas send us round in circles of imaginary worlds without telling us anything about a mind independent external world.

Philosophers agree these examples are analytic a priori. However, I can argue that relations of ideas which then from experience can be shown to be true are actually analytic a posteriori, which both rationalists and empiricists deny the existence of (Georges Dicker, 1998). The following deductive argument proves my point:

‘A bachelor is an unmarried man’ is an analytic statement.

Finding out if bachelors exist in the mind dependent external world instead of as a mental idea requires experience of bachelors Therefore knowing that bachelors exist in the mind independent external world is analytic a posteriori

This point is a not a mere triviality. It allows us to know all sorts off things about the world. For example take the analytic statement, ‘it is either raining here or it isn’t’. This can be derailed from the useless a priori circuit by checking reality. If one does understand the meaning of ‘rain’ one can easily find out it if is true or not by looking and feeling for rain and looking for clouds overhead. If I were to invent a new word; ‘frogging,’ meaning ‘there are frogs falling from the sky’, it is hard to see how someone cannot know if it is frogging outside or not.

Problem of Language

However, definitions of words can be subject to objection. For example a hermaphrodite, cross-dresser, or some who considers themselves of a different gender to what their biological sex indicates may disagree with being called a bachelor. A devout traditionalist Christian may disagree that a homosexual couple who are legally married are actually married ‘in the eyes of god’. To conclude this point, ‘bachelor’ refers to a group of people. That group will be slightly different to different people depending on their other beliefs. It depends on belief about what a man is and what marriage is. Every word in existence is an attempt to categorize what cannot be categorized. Language is not perfect, we can never know exactly what someone else means when they try to tell us something, so we can never truly understand a definition as it was intended and so we can never really understand a sentence that expresses relations of ideas. This does not mean we cannot know anything. It simply means we cannot express what we know to someone. I know it is not frogging outside, but you may not understand what frogging is despite my best efforts to explain. Words, sentences and indeed essays are all imperfect forms of communication. Knowledge does come in sentences. It comes in thoughts. Arguments for a mind independent external world

As I have mentioned, Hume pointed out that relations of ideas do not assert existence. This requires clarification. A correction would be to say that relations of ideas do not assert existence of the ideas but do assert existence of a mind dependent external reality. This is because if ideas are indeed combinations of impressions, then for a complex idea to exist, such as that of a Unicorn, there needs to have been certain original impressions to feed the imagination. The mind could not grasp the concept of any physical entity if it had not experienced an external reality where similar entities had existed. Dreaming and Descartes’ Cogito – showing there is an external reality

Everything has a cause. According to Descartes (Michael Moriarty, 2008) this is a clear and distinct perception, which means that while it is held in the mind it cannot be logically doubted. Our thoughts have a cause. We are not ‘giving birth’ to thoughts. Therefore there must be something external. Our senses may be wrong about what it is, and our intellect wrong in disentangling the data, but there is something out there. Descartes’ cogito ergo sum (I think therefore I exist) can therefore be extended to “I think, therefore I exist, and so do stimuli.”

But what about in a dream? Descartes asks. I would reply that the memories are the stimuli, but the memory has to have been formed somewhere during a conscious reality, otherwise the thoughts would be coming from nowhere.

A human by definition means a person with a physical brain. To deny that is to say that all definitions I understand could be wrong and thus everything I think could be wrong. If all I am is a thinking thing that has entirely wrong thoughts, how do I still exist? Should I still exist?

The answer to these questions can be made very simple. I am not only a thinking thing. I have a physical body and a lot of the things I consider myself to know about the world, I do know. This is a case of referring to the best possible answer, which is a common defence of induction by rationalists.

A problem

If all we can know, without being forced to retreat to probability, is that “I exist”; what if “I” am all that exists? If that is the case then labelling myself “I” would be nonsensical. If only one thing exists and cannot be distinguished from anything else, does it actually exist?

I will attempt to answer this question. Material objects are defined by their purpose, not by the atoms they are composed of. An empty kettle is just pieces of plastic and wiring put together to perform a function. When it is filled with water, it is still just a kettle. If I salivated into the kettle it is still a kettle and it would not be me. Everything has an action that can either be done to it, or that it can do itself. Collectively everything in the Universe may have one single grand function, but that grand function can be divided up. If I am all I know exists and my sensory data is just a part of me, I fit the definition of god of my reality. I am omnipresent, I am benevolent in that I want the best for me, I am the creator of (my) reality - even if that is done subconsciously, I am omnipotent in that I can do anything imaginable with my imagination. I am omniscient in that everything I know is all there is that can be known presently in my reality. Therefore I can choose how to divide up the functions of objects. I have attempted to put is in the form of a deductive argument:

Everything I experience I experience in my mind I am my mind

I am god


I have explained why people cannot truly know propositions that are made by someone else due to the problem of language. I have explained how a person can know they exist and that stimuli exist. I have explained how stimuli and the person cannot be easily separated and concluded that they are the same thing and so a person is god of their own reality and therefore can know things about it.


Descartes, R, translated by Michael Moriarty, (2008) Meditations on First Philosophy with selections from the Objections and Replies, (Oxford University Press)

Dicker, G, (1998) Hume’s Theory of Knoweldge 1, (London, Routledge)

Hume, D, (1739) An Enquiry Concerning Human Understanding (published at by the Leeds Electronic Text Centre)


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