Tutorial # 2. Why Be Moral. The Immoralist Challenge. Trasymachus' Argument

In the first book of Plato's Republic Thrasymachus presents Socrates with the immoralist's challenge.

P1 The consequences of being moral can be disastrous for one's happiness, (e.g. imprisonment, torture, poverty, and death).
P2 By contrast, the intended consequences of immorality are highly desired components of happiness (e.g. power, wealth, and honor) (343a- 344c).
Therefore, we should not be moral if we want to be happy.
Moral people must be simpleminded; they cannot be wise (348b-d).

In the first book of the Republic, Thrasymachus attacks Socrates’ position that justice is an important good. He claims that ‘injustice, if it is on a large enough scale, is stronger, freer, and more masterly than justice’ (344c).
Thrasymachus makes three central claims about justice.
1. Justice is nothing but the advantage of the stronger (338c)
2. Justice is obedience to laws (339b)
3. Justice is nothing but the advantage of another (343c).

Here is Trasymachus' argument:

P1 The ruling group or person is the stronger of the parts of a society.
P2 In a tyranny the tyrant passes laws to his\her advantage.
P3 In an aristocracy aristocrats pass laws to their advantage.
P4 In a democracy the (ruling) masses pass laws to their advantage.
There are no other types of regime.
Therefore, The ruling part of any nation passes [and enforces] laws that are to its own advantage.

P5 Every ruling party defines justice as obeying the law
P6 All ruling parties agree on defining justice as obeying the law is the correct definition.
Hence, justice is obeying the law.

Justice is everywhere to the advantage of the ruling party.
Justice is everywhere [to] the advantage of the stronger.