Thus, all we know and all we ever shall know of the world of matter and of minds must rest ultimately upon observation,—­observation of external things and of our own mind.  We must clip the erratic wing of a “reason” which seeks to soar beyond such knowledge; which leaves the solid earth, and hangs suspended in the void.

“But hold,” exclaims the critical reader; “have we not seen that Locke, as well as Descartes (section 48), claims to know what he cannot prove by direct observation or even by a legitimate inference from what has been directly observed?  Does he not maintain that the mind has an immediate knowledge or experience only of its own ideas?  How can he prove that there are material extended things outside causing these ideas?  And if he cannot prove it by an appeal to experience, to direct observation, is he not, in accepting the existence of the external world at all, just as truly as Descartes, a rationalist?”

The objection is well taken.  On his own principles, Locke had no right to believe in an external world.  He has stolen his world, so to speak; he has taken it by violence.  Nevertheless, as I pointed out in the section above referred to, Locke is not a rationalist of malice prepense.  He tries to be an empiricist.  He believes in the external world because he thinks it is directly revealed to the senses—­he inconsistently refers to experience as evidence of its existence.

It has often been claimed by those who do not sympathize with empiricism that the empiricists make assumptions much as others do, but have not the grace to admit it.  I think we must frankly confess that a man may try hard to be an empiricist and may not be wholly successful.  Moreover, reflection forces us to the conclusion that when we have defined empiricism as a doctrine which rests throughout upon an appeal to “experience” we have not said anything very definite.

What is experience?  What may we accept as directly revealed fact?  The answer to such questions is far from an easy one to give.  It is a harder matter to discuss intelligently than any one can at all realize until he has spent some years in following the efforts of the philosophers to determine what is “revealed fact.”  We are supposed to have experience of our own minds, of space, of time, of matter.  What are these things as revealed in our experience?  We have seen in the earlier chapters of this book that one cannot answer such questions off-hand.

62.  CRITICISM.—­I have in another chapter (section 51) given a brief account of the philosophy of Immanuel Kant.  He called his doctrine “Criticism,” and he distinguished it from “Dogmatism” and “Empiricism.”

Every philosophy that transcends experience, without first critically examining our faculty of knowledge and determining its right to spread its wings in this way, Kant calls “dogmatism.”  The word seems rather an offensive one, in its usual signification, at least; and it is as well not to use it.  As Kant used the word, Descartes was a dogmatist; but let us rather call him a rationalist.  He certainly had no intention of proceeding uncritically, as we shall see a little later.  If we call him a dogmatist we seem to condemn him in advance, by applying to him an abusive epithet.