Innate ideas and the principle of causality are explained very simply by the doctrine of the plurality of existences; they are, indeed, merely deductions from that doctrine. A man's soul, having already existed, either in the body of an animal or that of another man, has preserved the trace of the impressions received during that existence. It has lost, it is true, the recollection of actions performed during its first incarnation; but the abstract principle of causality, being independent of the particular facts, being only the general result of the practice of life, must remain in the soul at its second incarnation. Thus, the principle of causality, of which French philosophy cannot offer any satisfactory theory, is explained in the simplest possible manner, by the hypothesis of re-incarnations and of the plurality of existences. We have previously alluded to memory, and explained its relation to re-incarnations, and the reasons why we are born without any consciousness of a previous life. We have said, that if we come from an animal, we have no memory, because the animal has none, or has very little. We must now add, that if we come from a human soul, reopening to the light of life, we are destitute of memory, because it would disturb the trial of our terrestrial life, and even render it impossible, as it is the intention of nature that we should recommence the experience of existence without any trace, present to our minds, of previous actions which might limit or embarrass our free will. We cannot pass from this portion of our subject without calling attention to the fact that the remembrance of a previous existence is not always absolutely wanting to us. Who is there, who, in his hours of solitary contemplation, has not seen a hidden world come forth before his eyes from the far distance of a mysterious past? When, wrapped in profound reverie, we let ourselves float on the stream of imagination, into the ocean of the vague, and the infinite, do we not see magic pictures which are not absolutely unknown to our eyes? do we not hear celestial harmonies which have already enchanted our ears? These secret imaginings, these involuntary contemplations, to which each of us can testify, are they not the real recollections of an existence anterior to our life here below? Might we not also attribute to a vague remembrance, to an unconscious sympathy, the real and profound pleasure which we derive from the mere sight of plants, flowers, and vegetation? The aspect of a forest, of a beautiful meadow, of green hills, touches us, moves us, sometimes even to tears. Great masses of verdure, and the humble field daisy, alike speak to our hearts. Each of us has a favourite plant, the flower whose perfume he loves to inhale, or the tree whose shade he prefers. Rousseau was moved by the sight of a yew tree, and Alfred de Musset loved the willows so much, that he expressed a wish, piously fulfilled, that a willow might over-shadow his grave.