This gives the doctrine of 'indissoluble association'--the pivot of the whole scheme--the doctrine, says J. S. Mill, which, 'if it can be proved, is the greatest of all the triumphs of the Association Philosophy.'[542] The younger Mill always insisted upon the vast importance of the principle; but he here admits a difficulty. In a long note[543] upon James Mill's chapter on 'Belief,' conspicuous for his usual candour, he confesses the inadequacy of his father's view. The comment indicates the point of divergence and yet shows curiously the ground common to both. James Mill's theory states facts in some sense undeniable. Our 'ideas' cohere and combine to form a tissue: an imagery or series of pictures which form the content and are somehow the ground of our beliefs. The process of formation clearly involves 'association.' The scent of the rose is associated with the colour: both with the visible form and so forth. But is this process the same thing as believing, or have we to explain the belief by some mental activity different from, however closely connected with, the imagination, or in his phrase the 'ideation'? Here J. S. Mill finds a difficulty. The statement, 'I believe that thunder will follow lightning,' is something more than the statement, 'the sight suggests or calls up the sound.' The mental picture considered by itself may be described as a fact, without considering what belief, or whether any belief, is implied. J. S. Mill therefore makes a distinction intended to clear up his father's confusion. There is a difference, he says, between remembering 'a real fact' and remembering a 'thought.'[544] He illustrates this by the difference between the idea of Lafayette and the idea of Falstaff. Lafayette was real, and had been seen by the rememberer. Falstaff is a figment who, having never existed, can never have been seen. Yet the idea of Falstaff may be quite as vivid as the idea of Lafayette. What, then, is the difference between the two states of mind? One, says J. S. Mill, is a belief about 'real facts'; the other about 'thoughts.' This, he observes, corresponds to James Mill's distinction between a 'sensation' and an 'idea,'[545] a difference which he had admitted to be 'primordial.' Then, says J. S. Mill, we may as well admit that there is an 'element' in the remembrance of a real fact not implied in the remembrance of a thought and not dependent on any difference in the 'ideas' themselves. It, too, may be taken as 'primordial,' or incapable of further analysis. This doctrine becomes important in some of Mill's logical speculations,[546] and is connected with his whole theory of belief in an external world. It has an uncomfortable likeness to Reid's 'common-sense' view, and even to the hated 'intuitionism'; and Mill deserves the more credit for his candour.