Nina asked:

In my Philosophy class we were asked to answer this question…

If you can’t prove that anything exists outside your mind, is it all right to go on believing in the external world anyway?

I am so confused with this whole external world concept!

Answer by Jürgen Lawrenz

Your confusion is easily ameliorated. It is, in the first place, engendered by a stringent notion of absolute certainty. In the second place, by an unwarranted and indeed unprovable instrumental interpretation of existence. Once you put these aside as mere (though intriguing) speculation, you can plant your feet on the ground and prove, beyond the slightest doubt, that ‘nothing is in the mind that was not previously in the senses.’ This sentence was written 2500 years ago by Democritus and remains as true today as ever.

What it means is that the contents of your mind are like a flower that springs up from a seed and grows by exercising its capacity for self-nurture from nutrition in the environment, sunlight, water etc.. In technical lingo the mind’s nurture is called ‘priming’. Apart from a few survival skills passed on by the parents to their offspring, there is nothing in the mind at birth. But your mind has the capacity for responding to sensory information and to imprint these impressions on memory. As more and more stimuli accumulate, discrimination grows, judgements are formed and the infant acquires ‘knowledge’. You will not doubt understand that the pathway of this information is from the ‘outside world’, via the sensory conduits, to the appropriate neural cortices. Therefore an outside world has to exist prior to your accumulation of facts, features and knowledge of this world.

In fact, the only curious issue here is that the question in your statement is stated back to front. Rather than proving that an ‘outside world’ exists, you should ask if you can prove that any world can exist ‘in’ your mind. The answer is ‘No’. Every human being has a unique image of that world. We only know what’s ‘inside’ by the consensus of many people that your ‘inner’ world corresponds to everyone’s ‘inner world’, except in the trivial detail of their own location and environment.

In a word, don’t fall for assumptions that have no plausibility behind them. We are not inside the Matrix, but in a world that is real. Just think of all the other creatures whose evolution depends on them making correct inferences and judgements for survival. You are not unique or alone!


Answer by Helier Robinson

The external world concept is confusing until you understand its two meanings. One meaning is the empirical world that we all perceive around us, and which is external our heads. The second meaning arises with the claim, which may or may not be true, that everything that we are conscious of, including the empirical world, is in our minds, and our minds are in our heads; and everything empirical is an image of reality, not reality itself; and reality itself is the external world, also called the noumenal world.

To understand this you must recognise that if everything perceived — everything empirical — is an image of something noumenal, then your own empirical head is an image of your noumenal head. Your noumenal head contains your noumenal brain which contains your empirical world which contains you empirical head. So if you go out on a sunny day than beyond the blue sky is the inside surface of your noumenal skull. Very, very shocking to common sense, but logically sound. In the past knowledge of the noumenal world was metaphysical; now it is mathematical theoretical science. So the answer to the question in your philosophy class is yes, it is all right to go on believing in the external world — the noumenal world — because of the success of science. You can continue to be commonsensical about the external world in everyday living, but to do so in philosophy is over simplification.