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Aristotle's

logic

of thought. The completeness of our knowledge depends on the extent and completeness of our experience. His manner of reasoning is by the syllogism, an argument consisting of three propositions, such that the concluding one follows of necessity from the two premises, and of which, indeed, the whole theory of demonstration is only an example. Regarding logic as the instrument of thought, he introduces into it, as a fundamental feature, the ten categories. These predicaments are the genera to which everything may be reduced, and denote the most general of the attributes which may be assigned to a thing.

Temporary

His metaphysics overrides all the branches of the physical sciences. It undertakes an examination of the postuand meta- lates on which each one of them is founded, deterphysics. mining their truth or fallacy. Considering that all science must find a support for its fundamental conditions in an extensive induction from facts, he puts at the foundation of his system the consideration of the individual; in relation to the world of sense, he regards four causes as necessary for the production of a fact—the material cause, the substantial cause, the efficient cause, the final cause. But as soon as we come to the Physics of Aristotle we see at once his weakness. The knowledge of his failure of his age does not furnish him facts enough whereon system. to build, and the consequence is that he is forced into speculation. It will be sufficient for our purpose to allude to a few of his statements, either in this or in his metaphysical branch, to show how great is his uncertainty and confusion. Thus he asserts that matter contains a triple form-simple substance, higher substance, which is eternal, and absolute substance, or God himself; that the universe is immutable and eternal, and, though in relation with the vicissitudes of the world, it is unaffected The Peripatetic philothereby; that the primitive force which gives sophy. rise to all the motions and changes we see is Nature; it also gives rise to Rest; that the world is a living being, having a soul; that, since every thing is for some particular end, the soul of man is the end of his body; that Motion is the condition of all nature; that the world has a definite boundary

Substance,
Motion,
Space, Time.

The world.

and a limited magnitude; that Space is the immovable vessel in which whatever is may be moved; that Space, as a whole, is without motion, though its parts may move; that it is not to be conceived of as without contents; that it is impossible for a vacuum to exist, and hence there is not beyond and surrounding the world a void which contains the world; that there could be no such thing as Time unless there is a soul, for time being the number of motion, number is impossible except there be one who numbers; that, perpetual motion in a finite right line being impossible, but in a curvilinear path possible, the world, which is limited and ever in motion, must be of a spherical form; that the earth is its central part, the heavens the circumferential: hence the heaven is nearest to the prime cause of motion; that the orderly, continuous, and unceasing movement of the celestial bodies implies an unmoved mover, for the unchangeable alone can give birth to uniform motion; that unmoved existence is God; that the stars are passionless beings, having attained the end of existence, and worthy above other things of human adoration; that the fixed stars are in the outermost heaven, and the sun, moon, and planets beneath the former receive their motion from the prime moving cause, but the planets are disturbed by the stars; that there are five elements-earth, air, fire, water, and ether; that the earth is in the centre of the world, since earthy matter settles uniformly round a central point; that fire seeks the circumferential region, and intermediately water floats upon the earth, and air upon water; that the elements are transmutable into one another, and hence many intervening substances arise; that each sphere is in interconnection with the others; the earth is agitated and disturbed by the sea, the sea by the winds, which are movements of the air, the air by the sun, moon, and planets. Each inferior sphere is controlled by its outlying or superior one, and hence it follows that the earth, which is thus disturbed by the conspiring or conflicting action of all above it, is liable to the most irregularities; that, since animals are nourished by the earth, it needs must enter into their composition, but that water is required to hold the earthy matters together; that every element must be

looked upon as living, since it is pervaded by the soul of the world; that there is an unbroken chain from the simple element through the plant and animal up to man, the different groups merging by insensible shades into one Organic another: thus zoophytes partake partly of the beings. vegetable and partly of the animal, and serve as an intermedium between them; that plants are inferior to animals in this, that they do not possess a single principle of life or soul, but many subordinate ones, as is shown by the circumstance that, when they are cut to pieces, each piece is capable of perfect or independent growth or life. Their inferiority is likewise betrayed by their belonging especially to the earth to which they are rooted, each root being a true mouth; and this again displays their lowly position, for the place of the mouth is ever an indication of the grade of a creature: thus in man, who is at the head of the scale, it is in the upper part of the body; that in proportion to the heat of an animal is its grade higher : thus those that are aquatic are cold, and therefore of very little intelligence, and the same may be said of plants; but of man, whose warmth is very great, the soul is much more excellent; that the possession of locomotion by an organism always implies the possession of sensation; that the senses of taste and touch indicate the qualities of things in contact with the organs of the animal, but that those of smell, hearing, and sight extend the sphere of its existence, and indicate to it what is at a distance: that the place of Physiological reception of the various sensations is the soul, conclusions. from which issue forth the motions; that the blood, as the general element of nutrition, is essential to the support of the body, though insensible itself: it is also essential to the activity of the soul; that the brain is not the recipient of sensations: that function belongs to the heart; all the animal activities are united in the last; it contains the principle of life, being the principle of motion; it is the first part to be formed and the last to die; that the brain is a mere appendix to the heart, since it is formed after the heart, is the coldest of the organs, and is devoid of blood; that the soul is the reunion of all the functions of the body: it is an energy or active essence; being neither body nor magnitude, it cannot have extension, for

thought has no parts, nor can it be said to move in space; it is as a sailor, who is motionless in a ship which is moving; that, in the origin of the organism, the male furnishes the soul and the female the body; that the body being liable to decay, and of a transitory nature, it is necessary for its well-being that its disintegration and nutrition should balance one another; that sensation may be compared to the impression of a seal on wax, the wax receiving form only, but no substance or matter; that imagination arises from impressions thus made, which endure for a length of time, and that this is the origin of memory; that man alone possesses recollection, but animals share with him memory-memory being unintentional or spontaneous, but recollection implying voluntary exertion or a search; that recollection is necessary for acting with design. It is doubtful whether Aristotle believed in the immortality of the soul, no decisive passage to that effect occurring in such of his works as are extant.

Causes of

failure.

Aristotle, with a correct and scientific method, tried to build up a vast system when he was not in possession of the necessary data. Though a very learned man, he had not sufficient knowledge; indeed, there Aristotle's was not sufficient knowledge at that time in the success and world. For many of the assertions I have quoted in the preceding paragraph there was no kind of proof; many of them also, such as the settling of the heavy and the rise of the light, imply very poor cosmic ideas. It is not until he deals with those branches, such as comparative anatomy and natural history, of which he had a personal and practical knowledge, that he begins to write well. Of his physiological conclusions, some are singularly felicitous; his views of the connected chain of organic forms, from the lowest to the highest, are very grand. His metaphysical and physical speculations-for in reality they are nothing but speculations-are of no kind of value. His successful achievements, and also his failures, conspicuously prove the excellence of his system. He expounded the true principles of science, but failed to apply them merely for want of materials. His ambition could not brook restraint. He would rather attempt to construct the universe without the necessary means than not construct it at all.

Aristotle failed when he abandoned his own principles, and the magnitude of his failure proves how just his principles were; he succeeded when he adhered to them. If anything were wanting to vindicate their correctness and illustrate them, it is supplied by the glorious achievements of the Alexandrian school, which acted in physical science as Aristotle had acted in natural history, laying a basis solidly in observation and experiment, and accomplishing a like durable and brilliant result.

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From Aristotle it is necessary to turn to Zeno, for the Peripatetics and Stoics stand in parallel lines. The social Biography of conditions existing in Greece at the time of Zeno. Epicurus may in some degree palliate his sentiments, but virtue and honour will make themselves felt at last. Stoicism soon appeared as the antagonist of Epicureanism, and Epicurus found in Zeno of Čitium a rival. The passage from Epicurus to Zeno is the passage from sensual gratification to self-control.

The biography of Zeno may be dismissed in a few words. Born about B.c. 300, he spent the early part of his life in the vocation of his father, who was a merchant, but, by a fortunate shipwreck, happily losing his goods during a voyage he was making to Athens, he turned to philosophy for consolation. Though he had heretofore been somewhat acquainted with the doctrines of Socrates, he became a disciple of the Cynics, subsequently studying in the Megaric school, and then making himself acquainted with Platonism. After twenty years of preparation, he opened a school in the stoa or porch in Athens, from which his doctrine and disciples have received their name. He presided over his school for fifty-eight years, numbering many eminent men among his disciples. When nearly a hundred years old he chanced to fall and break his finger, and, receiving this as an admonition that his time was accomplished, he forthwith strangled himself. The Athenians erected to his memory a statue of brass. His doctrines long survived him, and, in times when there was no other consolation for man, offered a support in their hour of trial, and an unwavering guide in the vicissitudes of life, not only to many illustrious Greeks, but also to some of the great philosophers, statesmen, generals, and emperors of Rome.

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