The philosopher that I find relevant to me and the present day world, would be Socrates. His passion was for moral reform, and he abandoned and early interest in natural science as irrelevant to questions of conduct and the purpose of life. He was fond of illustrating his teleological viewpoint from the crafts. A shoemaker must know what a shoe is and what it is before he starts to work. Similarly, if, as everyone agreed, there is any general human being as such. Only by knowing what this is can we hope to live rightly: "therefore virtue is knowledge.
Socrates laid no claim to this knowledge. His advantage lay only in awareness of his ignorance. He wished to persuade men to seek it with him, but was hindered by their delusion that they already possessed it hence his first task was destructive, to convince men of their ignorance. The Athenians classed him with the Sophists, who also said that men were ignorant, but there was an essential difference. The Sophists believed knowledge to be impossible, but Socrates saw it as an attainable goal.
Most men when asked what justice or courage was replied by enumerating instances. Socrates then pointed out that this was only the first of two necessary stages. To discover was justice is, instances of agreed just acts must first be collected, and secondly examined to discover the common quality by right of which they are called just. This, the "form" of justice, expressed in a definition, will be the answer to the question: "What is justice?" The method is inductive, and its outcome was to reduce all virtues, including justice, to an understanding of the true nature of good and evil. Armed with this understanding, Socrates believed, men would automatically choose the right: "No one errs voluntary." His constant exhortation was to "care for the soul" (psyche), and he introduced a novel conception of the soul as the whole rational and moral personality.