As the story of his life unfolds in The King Must Die, Theseus develops from a passionate youth who had a small grasp of life to a reserved and knowledgeable king. Although some of his outlooks have changed, he possesses many of the same characteristics all throughout his life - honor, the understanding of moira, a strong will and quick mind, and the ability to persevere. Without these characteristics, the reader must wonder whether or not Theseus would have survived some of the ordeals that life presented him. .
From the beginning of his life, Theseus senses that he is special. He does not question the possibility that he is Poseidon's son, but rather seeks proof of what he believes to be true. Theseus realizes at a very young age the price that must be paid to be a king. The fate of a king is not unknown - it is preordained. Theseus immediately understands the concept of moira when his grandfather explains it to him; he recognizes it as the finished shape of his fate. He knows that unlike our fate, which is set out before us beyond our control, moira symbolizes our destiny and that which we make of ourselves. He sees that he must act of his own accord for the gods do not control what we do within the bounds of our fate; yet, they will not be cheated out of fulfilling our moira. For example, when Theseus kills Kerkyon and becomes king in Eleusis, he knows that he was fated to do so, but he also knows that it is not his moira to be in Eleusis. Thus, he follows the messages of the gods (mainly Poseidon) and trusts them to lead him when he is unsure of his fate.
Though he continually overcomes great obstacles and demonstrates tremendous abilities (whether by trusting Poseidon or himself), Theseus always meets more difficult challenges. Theseus could have taken his uncle's advice and been content with his abilities apart from wrestling. His refusal to give up shows that he is a tenacious character.