John Stuart Mill, who was certainly and perhaps more than anything a careful logician, commences an exposition of the idealist thesis to which he was so much attached, by carelessly saying: "It goes without saying that objects are known to us through the intermediary of our senses....

The senses are equivalent to our sensations;"[4] and on those propositions he rears his whole system, "It goes without saying ..." is a trifle thoughtless.

I certainly think he was wrong in not testing more carefully the solidity of his starting point.
In the first place, this limit set to our knowledge of the objects which stimulate our sensations is only accepted without difficulty by well-informed persons; it much astonishes the uninstructed when first explained to them.

And this astonishment, although it may seem so, is not a point that can be neglected, for it proves that, in the first and simple state of our knowledge, we believe we directly perceive objects as they are.

Now, if we, the cultured class, have, for the most part,[5] abandoned this primitive belief, we have only done so on certain implicit conditions, of which we must take cognisance.