IB Philosophy 10.8.6 the Nature of the Self Notes

The Tripartite Soul as a Theory of the Self

Three Parts of the Soul

1. The tripartite soul (from Greek tripartitos, three-parted) is central to Plato’s accounts of both psychology and politics in the Republic.
2. Plato arrives at the tripartite division via the principle of opposites (436b–441c): one and the same thing cannot simultaneously have opposite properties in the same respect. Since one can simultaneously thirst yet refuse to drink, there must be distinct sources for the thirst (appetite) and the refusal (reason).
   1. When a person is thirsty but refuses to drink (e.g., because the water is poisoned), reason overrules appetite. This conflict proves they are distinct parts, not one unified whole.
3. As established in 10.8.1 (435b–441c), Plato divides the soul into three parts, reason (logistikon), spirit (thumoeides), and appetite (epithumetikon), proved by the principle of opposites: the same person cannot simultaneously desire and refuse the same thing without distinct sources of each impulse. Here we examine what this tripartite structure implies for personal identity, self-knowledge, and moral psychology.
4. The rational part (logistikon) reasons, deliberates, and seeks truth and the good. It is the highest part, aiming at what is best for the whole soul.
   1. When the spirited part (thumoeides) is properly trained, it allies with reason: a soldier who is scared but fights because reason judges that courage is called for is displaying spirit under reason’s direction.
5. The appetitive part (epithumetikon) is the source of bodily desires: hunger, thirst, lust, and the desire for money (as the means to satisfy bodily desires).
6. The spirited part explains why people feel indignation at injustice even when it does not harm them personally. It is also the source of ambition and the desire for honour.
   1. The appetitive part is by far the largest: it contains a multitude of desires (the "many-headed beast"). It has no natural concern for reason or the good, only for its own satisfaction.
   2. Plato illustrates its power through the story of Leontius (439e–440a), who, despite feeling revulsion (spirit siding with reason), cannot resist gazing at corpses by the roadside.

Personal Identity and Self-Knowledge

1. For Plato, the self is identified with reason: to know oneself is to know which part of the soul is in command. The philosopher’s identity is defined by rational governance of the soul.
   1. The philosopher is defined by the rule of reason; the honour-lover by spirit; the money-lover by appetite. Who you are depends on which part of your soul governs the others.
2. This theory implies that self-knowledge is difficult and rare. Most people do not understand which part of the soul drives their choices. They mistake appetitive desire for reasoned judgment.
   1. Genuine self-knowledge is not merely introspection but rational diagnosis: identifying which part rules and whether this is appropriate.
3. A key implication is that most people do not know themselves in the relevant sense: they are driven by appetite or unchecked spirit without recognising it.
   1. This connects to the Allegory of the Cave: the prisoners do not know they are prisoners. Similarly, those ruled by appetite do not know they are not free.
4. Plato’s account also raises the question of personal identity over time: if the soul can change its governing part (as in character development), does personal identity remain constant?
   1. Plato’s answer is that the true self is reason: to the extent one’s rational part remains continuous and in command, one remains the same person.

The Self, the Body, and the Immortality of the Soul