8. This ‘thinking thing,’ then, as he finds it in himself, the philosopher, according to Locke, has merely and passively to observe, in order to understand the nature of knowledge. ‘I could look into nobody’s understanding but my own to see how it wrought,’ he says, but ‘I think the intellectual faculties are made and operate alike in most men. But if it should happen not to be so, I can only make it my humble request, in my own name and in the name of those that are of my size, who find their minds work, reason, and know in the same low way that mine does, that the men of a more happy genius will show us the way of their nobler flights.’ (Second Letter to Bishop of Worcester.) As will appear in the sequel, it is from this imaginary method of ascertaining the origin and nature of knowledge by passive observation of what goes on in one’s own mind that the embarrassments of Locke’s system flow. It was the function of Hume to exhibit the radical flaw in his master’s method by following it with more than his master’s rigour. Is such observation possible? 9. As an observation of the ‘thinking thing,’ the ‘philosophy of mind’ seems to assume the character of a natural science, and thus at once acquires definiteness, and if not certainty, at least plausibility. To deny the possibility of such observation, in any proper sense of the word, is for most men to tamper with the unquestioned heritage of all educated intelligence. Hence the unpalatability of a consistent Positivism; hence, too, on the other side, the general conviction that the Hegelian reduction of Psychology to Metaphysics is either an intellectual juggle, or a wilful return of the philosophy, which psychologists had washed, to the mire of scholasticism. It is the more important to ascertain what the observation in question precisely means. What observes, and what is observed? According to Locke (and empirical psychology has never substantially varied the answer) the matter to be observed consists for each man firstly in certain impressions of his own individual mind, by which this mind from being a mere blank has become furnished--by which, in other words, his mind has become actually a mind; and, secondly, in certain operations, which the mind, thus constituted, performs upon the materials which constitute it. The observer, all the while, is the constituted mind itself. The question at once arises, how the developed man can observe in himself (and it is only to himself, according to Locke, that he can look) that primitive state in which his mind was a ‘tabula rasa.’ In the first place, that only can be observed which is present; and the state in question to the supposed observer is past. If it be replied that it is recalled by memory, there is the farther objection that memory only recalls what has been previously known, and how is a man’s own primitive consciousness, as yet void of the content which is supposed to come to it through impressions, originally known to him? How can