91. Lamennais writes: "Who can say that a sixth sense would not disturb the harmony of the others by a contrary impression? On what foundation could he deny it? If we suppose other senses different from those which nature gave us, might not our sensations and our ideas be different? Perhaps a slight modification in our organs would be sufficient to ruin our whole science. Perhaps there are beings so organized that their sensations are wholly opposed to ours, and what is true for us is false for them, and reciprocally. For, if we examine the matter closely, what necessary connection is there between our sensations and the reality? And if there were such a connection, how could the senses make it known to us?"[38] [38] Essai sur l'Indifference, Tome II., Part III., Ch. I. The questions which these words raise are of the highest importance and merit a serious examination. 92. Is there any intrinsical impossibility of an organization different from ours, and an order of sensations different from those which we experience? It seems not; and if this impossibility exists, it is unknown to man. Whatever opinion we adopt as to the manner in which external objects act upon the soul by means of the organs of the body, there is no necessary relation, nor even analogy, between the object and the effect which it produces in us. A body receives upon its surface rays of the fluid which we call _light_, these rays are reflected upon the retina, which is another surface in communication with the brain. So far all is well, and easily understood. There is a fluid which moves, goes from one surface to another, and may cause this or that purely physical effect on the cerebral matter; but what connection is there between this and the impression of a distinct order which we call _seeing_, an impression which is neither the fluid nor the motion, but an affection of which the living and thinking being, the _me_ is intimately conscious? If, instead of the luminous fluid and its mechanism, we suppose another, as, for example, the air which vibrates upon the tympanum, what _essential_ reason is there why this should not produce a sensation similar to that of sight? It must be confessed that it is impossible to assign an _essential_ reason. To one who has no idea of our present organization, both phenomena are equally incomprehensible.