To the psychologist, then, the minds he studies are _objects_, in a world of other objects. Even when he introspectively analyzes his own mind, and tells what he finds there, he talks about it in an objective way. He says, for instance, that under certain circumstances the color gray appears to him green, and calls the appearance an illusion. This implies that he compares two objects, a real color seen under certain conditions, and a mental perception which he believes to represent it, and that he declares the relation between them to be of a certain kind. In making this critical judgment, the psychologist stands as much outside of the perception which he criticises as he does of the color. Both are his objects. And if this is true of him when he reflects on his own conscious states, how much truer is it when he treats of those of others! In German philosophy since Kant the word _Erkenntnisstheorie_, criticism of the faculty of knowledge, plays a great part. Now the psychologist necessarily becomes such an _Erkenntnisstheoretiker_. But the knowledge he theorizes about is not the bare function of knowledge which Kant criticises--he does not inquire into the possibility of knowledge _überhaupt_. He assumes it to be possible, he does not doubt its presence in himself at the moment he speaks. The knowledge he criticises is the knowledge of particular men about the particular things that surround them. This he may, upon occasion, in the light of his _own_ unquestioned knowledge, pronounce true or false, and trace the reasons by which it has become one or the other. It is highly important that this natural-science point of view should be understood at the outset. Otherwise more may be demanded of the psychologist than he ought to be expected to perform. A diagram will exhibit more emphatically what the assumptions of Psychology must be: ------------------------------------------------------------------------ | 1 | 2 | 3 | 4 | | The | The Thought | The Thought's | The Psychologist's | | Psychologist | Studied | Object | Reality | ------------------------------------------------------------------------ These four squares contain the irreducible data of psychology. No. 1, the psychologist, believes Nos. 2, 3, and 4, which together form _his _ total object, to be realities, and reports them and their mutual relations as truly as he can without troubling himself with the puzzle of how he can report them at all. About such _ultimate _ puzzles he in the main need trouble himself no more than the geometer, the chemist, or the botanist do, who make precisely the same assumptions as he.[187]