84. Necessary And Contingent

I pick up a rock from the ground and I let it go. It falls back to the ground. I pick it up again, and I let it go again. It still falls to the ground. I repeat the process several more times. The rock falls to the ground every single time. I conclude that the rock will always fall to the ground. This process of reasoning is called induction.

Induction is the foundation of our empirical knowledge. Insofar as all other kinds of knowledge can be traced back to empirical knowledge, it might even be the foundation of everything we know. We observe something happening over and over again without fail and then we infer it must be a significant truth about the world. In the case of the rock falling to the ground each and every time, we label this truth “the law of gravity”.

Why does induction work? It works because the world seems to have a certain regularity over time: the rock will fall to the ground in the very same way today, tomorrow, and every other day. What guarantees this regularity? Nothing at all. It is itself something we have observed over and over about the world, but we cannot justify the principle of induction using induction itself.

Still, our assumption of regularity seems to be holding up fine so far. There is no particular reason to doubt it. But we must be aware that regularity is not guaranteed. Regularity is a contingent fact about the world, which means the world could always be otherwise. If regularity is contingent then inductive reasoning is also contingent. And if induction is the foundation of all knowledge, then it follows that everything we know is contingent.

The opposite of contingency is necessity. Necessity implies that the world could not be otherwise — it must necessarily be exactly this. Any sense of necessary truths can be established only because we take regularity to be necessary in practice. But we need not do this. And that paradoxically means that necessity itself is contingent, while contingency seems to be necessary.