Parallel with the range of functions from sensation to reason there is a similar sequence from desire to will. All living creatures have some degree of conation, some innate will to live, which Aristotle calls orexis. This is the dynamic aspect of behaviour. It coexists with the different degrees of knowledge and so acquires different values. When the object which gives satisfaction is pre sented to the senses the tendency to possess it is the simplest form of orexis, called by the Latin writers appetitus and in Eng lish appetite. If the want or striving is correlated with an image of the object desired or the object is the work of imagination, the psychological state is called wish. If finally the object is one about which it is possible to deliberate, the outcome of delibera tion is called will. Here we find Aristotle using his principle of de velopment to state in simple terms a naturalistic theory of will. There is no suggestion that will is a separate faculty and no dis cussion of freedom of the will. Aristotle defines will simply as that desire which embodies the results of deliberation and dis cusses individual responsibility, but not freedom of the will. He considers also the difference between those who do not stop to deliberate and those who tend to paralyse action by excessive deliberation. These are the types known to modern writers as impulsive and obstructive. These topics were regarded by Aris totle as belonging to the science of conduct and are discussed in his Ethics. The word ethics is derived from the word meaning char acter (ethos) and this is a variation of the word for habit (ethos). The Greek sense for individual qualities made their ethics prima rily a study of character and therefore a branch of psychology. The keynote of individual development is habit-formation and Aris totle's ethics has for its centre a doctrine of character as the product of habits. The habit is not mechanical: it is a disciplined attitude of mind which makes the act of judgment an expression of principles : morality is dependent on reason and reason can only act efficiently when impulses are properly organized.
This brief and summary statement will serve to indicate how far Aristotle covered the whole field of psychology. His treat ment of knowing and willing as the main classes of functions re mained with little alteration for many centuries. Such subjects as sleep and dreams he treated in a scientific manner, and showed an interest in abnormal phenomena. His successors in the Peri patetic school tended more and more towards purely scientific work. The first head of the school after Aristotle was Theophras tus whose fame rests chiefly on his work in botany but is sup ported also by the fragments of a work on the senses. This is exclusively concerned with questions that belong to empirical psychology and seems to show an increasing tendency to separate this subject from the sphere of speculative philosophy or re ligion.
With the death of Alexander in the year 323 B.C. the Hellen ,istic Age began and with it there came a period of speculative thinking more Oriental than Greek in its character. On the other hand at Alexandria itself the sciences began a triumphant progress which soon eclipsed all previous efforts. The greatest scientific achievements of antiquity belong to the third century before Christ and show that religion was by no means the only interest of that age. In addition to the work done in geometry, astronomy, mechanics and other sciences, special mention should be made of the work of the medical men Herophilus and Erasistratus. Though these men were not the first to discover the nerves, they so far enlarged and established the knowledge of their structure and function that they deserve to be called the discoverers of the nervous system. This was a great contribution to the knowl edge of animal organisms and one which in the end could not fail to affect psychological theory. At the time it produced no revolu tion. The Stoic philosophers used the pneuma of their predeces
sors and showed considerable skill in the analysis and classifica tion of functions. Though their interests were mainly ethical the earlier Stoics (c. 30o B.c.) took pains to elaborate their psycho logical basis. They seem to have realized more clearly than their predecessors that psychologically a sensation is only an event in consciousness, a mere awareness of an inner state : they em phasized the relation between imagination (fantasy) and halluci nation (phantasm) with the associated problem of the relation between subjective conviction (illusion) and objective truth. The Stoics delighted in extravagances and talked about universal Reason or Logos : but out of much speculation they evolved some important ideas. Because reason was to some degree innate in all creatures they attributed to animals an unreflective wisdom which was known to the Roman Stoics as instinct. Similarly from the belief that all men were endowed by nature with a knowledge of natural laws and rights they derived the concept of conscience (syneidesis), the inner sense of conformity or lack of conformity with this innate reason.
The extraordinary brilliance of the classical period of Greek thought was neglected for nearly five centuries after its decline. The Stoics carried on the work when Greece became a Roman province, but their power was soon exhausted and their history became a record of mere repetitions. The only factors that had any significance in the Hellenistic Age were the various religious movements which tended to create a division between the natural and supernatural elements in the description of man. The Jews of Alexandria in the last century before Christ adopted the lan guage and ideas of the Greeks but recognized the sphere of scientific investigation as relevant only to the corporeal nature : the spiritual life was not to be studied by such methods. As the Hebrew tradition always distinguished between the vital prin ciple and the supernatural spirit (neshem and ruah) this method of adopting Greek psychology to explain the facts of sense experience was easily adapted to the general body of their thought. Philo Judaeus (c. A.D. 40) was the most effective author of this Jewish-Alexandrian School. The same principles were followed by the Christian Platonists of Alexandria (about A.D. i8o) and in this way a large amount of pagan teaching became established as part of the tradition of the Christian schools. In the third century of the Christian era the pagan philosophy was revived by Plotinus. While this was definitely intended to be a return to Platonism it was so far affected by the spirit of the age that it emphasized primarily the inner experience and made its psy chology a description of those activities of the soul which seemed to be independent of bodily processes. A pure psychology built on introspective study of such phenomena as attention and memory was the result. The influence of Plotinus was continued in the work of Augustine ; and through the position of authority which Augustine retained in the Middle Ages, this type of intro spective thought was never wholly forgotten. The development of ancient psychology may be said to have concluded in a separa tion between the physiological and the religious interests. Galen (A.D. 20o) was the last great physician. He added to the knowl edge of the nerves by distinguishing sensory from motor nerves and made some acute observations on the relation between mind and body. Galen was sufficiently interested in philosophy to discuss many questions which belong to the field of physiological psychology, but always from the point of view of the medical man. Augustine (d. A.D. 43o) studies the problems of psychology from the standpoint of an observer who can describe the actual experiences. The passages in the Confessions which describe memory and spiritual exaltation are permanent contributions to the literature of psychology.