Note XXXIII., page [245].
Defects in the Organic World.
The objections to final causes from alleged defects in the organic world have been answered with wisdom and success by M. Janet, in his 'Causes Finales,' pp. 313-348.
The views of Professor Helmholtz as to the defects of the eye will be found stated at length in his popular lectures on scientific subjects. The chief defects enumerated are: 1. Chromatic aberration, connected with 2. Spherical aberration and defective centring of the cornea and lens, together producing the imperfection known as astigmatism; 3. Irregular radiation round the images of illuminated points; 4. Defective transparency; 5. Floating corpuscles, and 6. The "blind spot" with other gaps in the field of vision. "The eye has every possible defect that can be found in an optical instrument, and even some which are peculiar to itself." "It is not too much to say that if an optician wanted to sell me an instrument which had all these defects, I should think myself quite justified in blaming his carelessness in the strongest terms, and giving him back his instrument. Of course I shall not do this with my eyes, and shall be only too glad to keep them as long as I can—defects and all. Still, the fact that, however bad they may be, I can get no others, does not at all diminish their defects, so long as I maintain the narrow but indisputable position of a critic on purely optical grounds."
Helmholtz himself, however, points out that the defects of the eye are "all so counteracted, that the inexactness of the image which results from their presence very little exceeds, under ordinary conditions of illumination, the limits which are set to the delicacy of sensation by the dimensions of the retinal cones;" that "the adaptation of the eye to its function is most complete, and is seen in the very limits which are set to its defects." In fact, were the eye more perfect as an instrument of optical precision, it would be less perfect as an eye. Its absolute defects are practical merits. To be a useful eye it must be neither a perfect telescope nor a perfect microscope, but a something which can readily serve many purposes, and which can be supplemented by many instruments. The delicate finish of a razor renders it unfit for cutting wood. All man's senses and organs are inferior to those possessed by some of the lower animals, but the inferiority is of a kind which is a real and vast advantage. It is of a kind which allows them to be put to a greater variety of uses than could more perfect senses and organs. It is the very condition of their capacity to be utilised in manifold directions by an inventive and progressive reason. Further, no man can see at all merely with a so-called perfect optical instrument. He must have in addition the imperfect instrument, composed of a soft, watery, animal substance, and designated the eye. There is that in the eye which immeasurably transcends all mere physics and chemistry, all human mechanism and contrivance; there is life; there is vision.
Note XXXIV., page [252].
Epicurean Dilemma.
The Epicurean dilemma has been often dealt with. I shall content myself with quoting Mr Bowen's remarks on the subject: "Omnipotence and benevolence are apparently very simple and very comprehensive terms, though few are more vaguely used. The former means a power to do everything; but this does not include the ability to do two contradictory things at the same moment, or to accomplish any metaphysical impossibility. Thus, the Deity cannot cause two and two to make five, nor place two hills near each other without leaving a valley between them. The impossibility in such cases does not argue a defect of power, but an absurdity in the statement of the case to which the power is to be applied. A statement which involves a contradiction in terms does not express a limitation of ability, because in truth it expresses nothing at all; the affirmation and the denial, uttered in the same breath, cancel each other, and no meaning remains. All metaphysical impossibilities can be reduced to the formula, that it is impossible for the same thing to be and not to be at the same moment, as this would be an absurdity—that is, an absurd or meaningless statement. Thus, virtue cannot exist without free agency, because a free choice between good and evil is involved in the idea of virtue, so that the proposition means no more than this—that what contains freedom cannot be without freedom. We cannot choose between good and evil, unless good and evil are both placed before us—that is, unless we know what these words mean; and we cannot express our choice in action, unless we are able to act—that is, unless we have the power of doing either good or evil. In the dilemma quoted from Epicurus, a contradiction in terms is held to prove a defect of power, or to disprove omnipotence; the dilemma, therefore, is a mere logical puzzle, like the celebrated one of Achilles and the tortoise.