The unsuccessful struggle in which those persons engage, who attempt to throw off the impression of design in the creation, appears in an amusing manner through the simplicity of the ancient Roman poet of this school. Lucretius maintains that the eye was not made for seeing, nor the ear for hearing. But the terms in which he recommends this doctrine show how hard he knew it to be for men to entertain such an opinion. His advice is,-- Illud in his rebus vitium _vehementer_ et istum Effugere errorem, vitareque _præmeditator_, Lumina ne facias oculorum clara creata, Prospicere ut possimus. iv. 823. ’Gainst their preposterous error guard thy mind Who say each organ was for use design’d; Think not the visual orbs, so clear, so bright, Were furnish’d for the purposes of sight. Undoubtedly the poet is so far right, that a most “vehement” caution and vigilant “premeditation” are necessary to avoid the “vice and error” of such a persuasion. The study of the adaptations of the human frame is so convincing, that it carries the mind with it, in spite of the resistance suggested by speculative systems. Cabanis, a modern French physiological writer of great eminence, may be selected as a proof of this. Both by the general character of his own speculations, and by the tone of thinking prevalent around him, the consideration of design in the works of nature was abhorrent from his plan. Accordingly, he joins in repeating Bacon’s unfavourable mention of final causes. Yet when he comes to speak of the laws of reproduction of the human race, he appears to feel himself compelled to admit the irresistible manner in which such views force themselves on the mind. “I regard,” he says, “with the great Bacon, the philosophy of final causes as barren; but I have elsewhere acknowledged that it was very difficult for the most cautious man (l’homme le plus reservé) never to have recourse to them in his explanations.”[41] 3. It may be worth our while to consider for a moment the opinion here referred to by Cabanis, of the propriety of excluding the consideration of final causes from our natural philosophy. The great authority of Bacon is usually adduced on this subject. “The handling of final causes,” says he, “mixed with the rest in physical inquiries, hath intercepted the severe and diligent inquiry of all real and physical causes, and given men the occasion to stay upon these satisfactory and specious causes, to the great arrest and prejudice of farther discovery.”[42]