Whenever one representation is linked to another and represents that link within itself, there is a sign: the abstract idea signifies the concrete perception from which it has been formed (Condillac); the general idea is no more than a particular idea serving as a sign for other particular ideas (Berkeley); imaginings are signs of the perceptions from which they arose (Hume, Condillac); sensations are signs of one another (Berkeley, Condillac); and, finally, it is possible that sensations may themselves be (as in Berkeley) signs of what God wishes to tell us, which would make them, as it were, signs for a complex of signs.