The best of all possible worlds
So far all we have done is to say that for everything that is true, there must be a reason why it is true, and that in the case of a necessary truth that reason lies in the Principle of Contradiction. But most of the things we want to explain are simple contingencies – things which are true, but which might have been false; as Leibniz puts it, things which are true in this actual world in which we live, but which in other worlds which might have existed – in other possible worlds – could have been false. Why did it rain today? Why did my child die? How do trees know it’s time to drop their leaves? Why does E = MC2? Why are we here, and what is it all for? Leibniz doesn’t pretend that he knows the answer to all these questions, of course; but he does claim that he knows the form which the answers to them must take; he knows the general kind of Sufficient Reason which must ultimately be given for contingent truths.