This objection does not only hold against the eclectics, but also against the Scottish school and the ideologists. We already find it set forth in a letter from Comte to Valat on the 24th, of September, 1819, when he was perhaps not yet acquainted with Cousin. “With what should we observe the mind itself, its operations, its activity? We cannot divide our mind, that is to say, our brain, into two parts, of which one acts while the other looks on, to see how it goes to work. The so-called observations made on the human mind, considered in itself and _a priori_, are pure illusions. All that we call _logic_, _metaphysics_, _ideology_, is an idle fancy and a dream, when it is not an absurdity.”[182] This text, to which we could add many similar ones, allows us to rectify an erroneous, although a frequent interpretation of Comte’s thought. He does not deny that we are informed by consciousness of the existence of psychical phenomena. On the contrary, he expressly recognises the fact. What he regards as impossible is to study the activity of thought by means of reflection, that is to discover the “intellectual laws” by a method of internal observation. In a word, it is such works as those of Condillac, of the ideologists, of Reid, etc., which he condemns in their principle. In these works the subject matter is the theory of knowledge, and not that which is called to-day _psychology_ proper. If, instead of seeking specially for the intellectual laws, we wish to study psychical phenomena in general, internal observation will become possible in a certain number of cases. But it will not lead to the end which we wish to reach. It excludes the use of the comparative method, so fertile and so indispensable in the whole domain of biology. It only studies man, and even adult and healthy man. What will it tell us of the child, of the mentally deranged, of the animal?[183] Will it, like Descartes, go so far as to deny the existence of a psychical life in animals? Still this life cannot be studied by internal observation. We must then have recourse to another method.