But it is a psychological fact none the less true, and one to which the philosophers have paid too little attention, that habit, like a second nature, has the power of fixing in the mind new categorical forms derived from the appearances which impress us, and by them usually stripped of objective reality, but whose influence over our judgments is no less predetermining than that of the original categories.Hence we reason by the ETERNAL and ABSOLUTE laws of our mind, and at the same time by the secondary rules, ordinarily faulty, which are suggested to us by imperfect observation.This is the most fecund source of false prejudices, and the permanent and often invincible cause of a multitude of errors.The bias resulting from these prejudices is so strong that often, even when we are fighting against a principle which our mind thinks false, which is repugnant to our reason, and which our conscience disapproves, we defend it without knowing it, we reason in accordance with it, and we obey it while attacking it.Enclosed within a circle, our mind revolves about itself, until a new observation, creating within us new ideas, brings to view an external principle which delivers us from the phantom by which our imagination is possessed.
Thus, we know to-day that, by the laws of a universal magnetism whose cause is still unknown, two bodies (no obstacle intervening) tend to unite by an accelerated impelling force which we call GRAVITATION.It is gravitation which causes unsupported bodies to fall to the ground, which gives them weight, and which fastens us to the earth on which we live.
Ignorance of this cause was the sole obstacle which prevented the ancients from believing in the antipodes."Can you not see,"said St.Augustine after Lactantius, "that, if there were men under our feet, their heads would point downward, and that they would fall into the sky?" The bishop of Hippo, who thought the earth flat because it appeared so to the eye, supposed in consequence that, if we should connect by straight lines the zenith with the nadir in different places, these lines would be parallel with each other; and in the direction of these lines he traced every movement from above to below.Thence he naturally concluded that the stars were rolling torches set in the vault of the sky; that, if left to themselves, they would fall to the earth in a shower of fire; that the earth was one vast plain, forming the lower portion of the world, &c.If he had been asked by what the world itself was sustained, he would have answered that he did not know, but that to God nothing is impossible.
Such were the ideas of St.Augustine in regard to space and movement, ideas fixed within him by a prejudice derived from an appearance, and which had become with him a general and categorical rule of judgment.Of the reason why bodies fall his mind knew nothing; he could only say that a body falls because it falls.
With us the idea of a fall is more complex: to the general ideas of space and movement which it implies, we add that of attraction or direction towards a centre, which gives us the higher idea of cause.But if physics has fully corrected our judgment in this respect, we still make use of the prejudice of St.
Augustine; and when we say that a thing has FALLEN, we do not mean simply and in general that there has been an effect of gravitation, but specially and in particular that it is towards the earth, and FROM ABOVE TO BELOW, that this movement has taken place.Our mind is enlightened in vain; the imagination prevails, and our language remains forever incorrigible.To DESCEND FROM HEAVEN is as incorrect an expression as to MOUNTTO HEAVEN; and yet this expression will live as long as men use language.
All these phrases--FROM ABOVE TO BELOW; TO DESCEND FROM HEAVEN;TO FALL FROM THE CLOUDS, &C.--are henceforth harmless, because we know how to rectify them in practice; but let us deign to consider for a moment how much they have retarded the progress of science.If, indeed, it be a matter of little importance to statistics, mechanics, hydrodynamics, and ballistics, that the true cause of the fall of bodies should be known, and that our ideas of the general movements in space should be exact, it is quite otherwise when we undertake to explain the system of the universe, the cause of tides, the shape of the earth, and its position in the heavens: to understand these things we must leave the circle of appearances.In all ages there have been ingenious mechanicians, excellent architects, skilful artillerymen: any error, into which it was possible for them to fall in regard to the rotundity of the earth and gravitation, in no wise retarded the development of their art; the solidity of their buildings and accuracy of their aim was not affected by it.But sooner or later they were forced to grapple with phenomena, which the supposed parallelism of all perpendiculars erected from the earth's surface rendered inexplicable: then also commenced a struggle between the prejudices, which for centuries had sufficed in daily practice, and the unprecedented opinions which the testimony of the eyes seemed to contradict.
Thus, on the one hand, the falsest judgments, whether based on isolated facts or only on appearances, always embrace some truths whose sphere, whether large or small, affords room for a certain number of inferences, beyond which we fall into absurdity.The ideas of St.Augustine, for example, contained the following truths: that bodies fall towards the earth, that they fall in a straight line, that either the sun or the earth moves, that either the sky or the earth turns, &c.These general facts always have been true; our science has added nothing to them.
But, on the other hand, it being necessary to account for every thing, we are obliged to seek for principles more and more comprehensive: that is why we have had to abandon successively, first the opinion that the world was flat, then the theory which regards it as the stationary centre of the universe, &c.
