Are the good and the true the same for Hobbes? It seems (to me) that they must be, and, in fact, I cannot conceive of them actually being any different. The clearest example where the two are different is Nietzsche, who rejects truth all together while supposing that man can still achieve his height of existence through that which is good (will to power). The clearest example of the good and the true being the same is Plato, for knowing the Good (the Truth) is the supposed highest form of life.
For Hobbes, it is debatable whether the good and the true and the same. When speaking of the right of the sovereign to be the judge of doctrine and opinion, he says that when doctrine is aimed at peace it is necessarily true (xviii, 9). Wishing to keep his commonwealth in a peaceful state, a (good) sovereign will reasonably offer doctrine of peace. And this doctrine is true because it is in accord with the first natural law (xiv, 4). So far so good – the truth and the good are one and the same.
Next, I wonder if a sovereign can reasonably lie to his subjects. Suppose god is not real, but the sovereign lies and says he (god) is. This is plausible, for Hobbes gives an account of Gentiles doing this same sort of thing to keep their people in obedience and peace (xii, 20). It seems reasonable to say, then, that:
A) the sovereign lies and says God is real
B) it promotes peace (as I believe Hobbes thinks it does)
Therefore, C) this a true doctrine
Obviously, since the first premise is a lie, this cannot be true. But since Hobbes has already conceded that it is plausible for a leader to imprint a false belief concerning divine ordination in his subjects’ minds, it is at least possible that Hobbes’ beliefs concerning God are also false. Hobbes would never agree to this (of course the Bible is true!), but perhaps it should set off alarms concerning the rigor of Hobbes’ account of truth.