ACADEMICS, a sect of philosophers, who followed the doctrine of Socrates and Plato, as to the uncertainty of knowledge, and the incomprehensibility of truth.
Academic, this sense, amounts to much the same with the differ ence between them being only i u point of time. They who embraced the system of Plato, among the ancients, were called Academici ; whereas those who have done the same, since the restoration of learn ing, have assumed the denomination of Piatonists. We usually reckon three sects of though some snake five. The ancient Academy was that which was founded by Plato ; and consisted of those followers of this eminent philosopher,who taught the doctrine of their master with out mixture or corruption. The first of these was Speusippus ; he was succeeded by Xenocrates. After his death the direc tion of the academy devolved upon Pole mo, andthen upon Crates, and terminated with Crantor. After the death of Crates, a new tribe of philosophers arose, who, on account of certain innovations in their manner of philosophising, which in some measure receded from the Platonic sys tem, without entirely deserting it, have been distinguished by the appellation of the Second, or Middle Academy. The first preceptor who appears in this class, and who, in consequence of the innova tions which he introduced into the Pla tonic school, has been commonly consi dered as the founder of this academy, is Arcesilaus. Before the time of Arcesi laus, it was never denied, that useful opi nions may be deduced from the senses. Two sects arose about this time, which threatened the destruction of the Platonic system one was founded by Pyrrho, which held the doctrine of universal scep ticism, and the other by Zeno, which main tained the certainty of` human knowledge, and taught with great confidence a doc trine essentially different from that of Plato. In this situation, Arcesilaus thought it necessary to exercise a cautious reserve with regard to the doctrine of his master, and to conceal his opinions from the vul gar, under the appearance of doubt and uncertainty. Professing to derive his doc trine concerning the uncertainty of know ledge from Socrates, Plato, and other philosophers, lie maintained, that though there is a real certainty in the nature of things, every thing is uncertain to the hu man understanding, and consequently that all confident assertions arc unreasonable. lIe thought it disgraceful to assent to any proposition, the truth of which is not fully established, and maintained, that in all questions, opposite opinions may be sup ported by arguments of equal weight.
Ile disputed against the testhnony of the senses, and the authority of reason ; ac knowledging., at the same time, that they furnish probable opinions sufficient for the conduct of life. However, his secret de sign seems to have been to establish the doctrine of Plato, that the knowledge de rived from sensible objects is uncertain, and that the only true science is that which is employed upon the immutable objects of intelligence, or ideas.
After the death of Arcesilaus, the Pla tonic school was successively under the care of Lacydes, who is said to have found ed a new school, merely because he changed the place of instruction, and held it in the garden of Attains, within the li mits of the Academic grove, and of Evan der and Egesinus. Arcesilaus, however, had opposed the Stoics, and other dogma tical philosophers,with such violence, and extended his doctrine of uncertainty so far, as to alarm not only the general body of philosophers, who treated him as a com mon enemy to philosophy, but even the governors of the state, who apprehended that his opinions would dissolve all the bonds of social virtue and ofreligion. His successors, therefore, found it difficult to support the credit of the academy ; and Carneades, one of the disciples of this school, relinquished, at least in words, sonic of the more obnoxious tenets of Ar cesilaus.
From this petiod the Platonic school assumed the appellation of the New Aca demy, which may be reckoned the third in order from its lirst establishment. It was the doctrine of this academy, that the senses, the understanding, and the imagi nation, frequently deceive us, and there fore cannot be infallible judges of truth ; but that, from the impressions produced on the mind, by means of the senses, call ed by Carneades phantasies, or images,we infer appearances of truth,orprohabilities. These images do not always correspond to the real nature of things, and there is no infallible method of determining when they are true or false ; and they afford no certain criterion of truth. But, with respect to the conduct of life, and the pursuit of happiness, probable appearances are a sufficient guide, be cause it is unreasonable not to allow some degree of credit to those witnesses who commonly give a true report.