Pullman and Plutarch

In his account of Alexander the Great, Plutarch (c. AD 46 - 120) states that Cleitus the Black, the Macedonian warrior who saved Alexander's life at the Battle of the Granicus River, was lead by his 'evil genius' to criticise the king in such a manner that caused Alexander to kill him.

In this context, 'evil genius' should not be taken to mean that Cleitus was a criminal mastermind. As the footnote points out, the ancients believed that at birth, every man received a 'daimon' which might be good or evil but which would stay with him for life. 

It seems to me that to understand what the daimon was we should turn to Philip Pullman's His Dark Materials books. In them, humans are accompanied by an animal - called their daemon - which is a physical manifestation of their soul. 

Although the daemons were not indicators of the individuals morality (although they might be more or less aggressive according to the person they came from) I think that Pullman must have borrowed the idea from the ancients. I wonder if anyone has any other ideas?