Plato argued that the ideal state – one which ensured the maximum possible happiness for all its citizens – could only be brought into being by a ruler possessed of absolute knowledge, obtained through philosophical study.
Several historical figures, including Marcus Aurelius and Ashoka the Great, have been described by ancient and modern writers as embodying the philosopher king ideal.
[7] Having returned to the subject of the ideal state, Socrates elaborates on the way in which his Guardians would be educated, in order to lead them to a full and total knowledge of the Forms.
Islamic scholars, on the other hand, were heavily influenced by Plato's Republic, finding in the philosopher king a counterpart to the traditional figure of the "lawgiver-prophet".
[11] Al-Farabi, for example, followed Plato closely, writing that the ideal state was that which most carefully attended to the spiritual education of its citizens, and that its ruler must therefore have a highly developed understanding of the purpose of human existence.
Biblical figures such as Moses, Abraham and Solomon were held up as examples of ideal rulers, with Plato's theory undergoing further distortions in order to meet the needs of Jewish philosophers.
The popularity of the idea finally declined during the seventeenth century, as influential authors such as Baruch Spinoza began to formulate more secular political philosophies modelled on the works of Machiavelli.
[14] It appears from the Republic that Plato did not think it impossible for his ideal state to be established in reality,[15] and he did make one notable attempt to educate a ruler in the principles of philosophy.
Not only was Archytas a distinguished Pythagorean philosopher, he was also a skilled military general and a popular political leader, serving seven terms as strategos in the city of Tarentum, Italy.
His contemporary Onesicritus spoke of him as a "philosopher in arms", and the 1st-century Platonist Plutarch wrote in laudatory terms of his wisdom, generosity, temperance and courage.
Plutarch's justification for calling Alexander a philosopher was that he had actualised principles which had previously only been spoken of as ideals and had "changed the brutish customs of countless nations".
Ancient sources such as the Historia Augusta call him "the philosopher" and praise him for the clemency of his reign, while his Stoic tome Meditations is still revered as a literary monument to a philosophy of service and duty.