John’s knowledge of his own anxiety would be in part the same as that of the other observers. He too would judge his condition by its external manifestations, would name its sort and rate its amount on the basis of his own behavior, as he saw his own face, heard his own groans, and read the notes he wrote describing his condition. But he would also, as with the toothache, have data from internal sense-organs and perhaps from centrally initiated neural actions. In so far as he could report these data to himself for use in scientific thought more efficiently than he could report them to the other observers, he would have, as with the toothache, an advantage comparable to the advantage of a criminologist who happened also to be or to have been a thief, or of a literary critic who happened to have written what he judged. It is important to note that only in so far as he who has ‘immediate experience’ of or participates in or is ‘directly conscious’ of the anxiety, reports it to himself as thinker or scientific student, in common with the other nineteen, that this advantage accrues. To really _be_ or _have_ the anxiety is not to correctly _know_ it. An insane man must become sane in order to know his insane condition. Bigotry, stupidity and false reasoning can be understood only by one who never was them or has ceased to be them. In our last illustration, John’s thinking of ‘9 × 7 equals 63,’ the effect on John’s behavior may be so complicated by other conditions in John, and is so subject to the particular conditions which we name John’s ‘will,’ that the observers would often be at loss except for John’s verbal report. Not that the observer is restricted to that. If John does the example 217 × 69 in the usual way, it is a very safe inference that he thought 9 × 7 equals 63, regardless of the absence of a verbal report from him. But often there is little else to go by. To John himself, on the contrary, it is easier to be sure that he is thinking of 9 × 7 equals 63, than that he has a particular sort and strength of toothache. Consequently if we suppose John to be thinking of that fact while under observation, and the twenty observers to be required to identify the fact he is thinking of, it is sure that there might be an enormous variability in their guesses as to what the fact was and that his testimony might be worth far more than that of all the other nineteen without his testimony. His observation is influenced by the action of the neurones in his central nervous system as theirs is not, and, in the case of the thought ‘9 × 7 equals 63,’ the action of these neurones is of special importance.