N.B. This is a chapter in a book about truth and knowledge. It is the first draft. I have since revised it. You can find the most up-to-date info/version on the book's website.

As we've explored in the preceding chapters, knowledge of the truth is fundamentally uncertain because it's ultimately grounded, not in itself or logic or observation, but in what we care about. And yet, truth appears to have a a solid foundation because we all care—to greater and lesser extents—about accurately predicting reality so that we can make it the way we want it to be. Thus, the normality of truth is preserved.

Normality not withstanding, the far reaching implications of the fundamentally uncertain nature of truth are subtle. They can defy intuitions and complicate that which seemed simple. Therefore, in this final chapter, I'll attempt to clarify three topics that many people find confusing when developing a deep understanding of fundamental uncertainty.

The Intersubjective Truth

There are, broadly speaking, two school of thought on the nature of truth. One says that truth is objective and exists independent of our knowledge of it. The other says that truth is subjective and always contingent on a mind doing the knowing. Which is right?

Objectivity has much to recommend it. The success of mathematics and science is largely due to them giving us tools for finding truth regardless of what any individual thinks. To wit, whether or not two plus two equals four or the speed of light in a vacuum is 299,792,458 meters per second seem unaffected by anything going on in our minds. If we one day meet aliens from another world, we expect their math and science to proclaim the same truths ours does. The universe, as best we can tell, exists independent of us, and what we think about it has no bearing on its truths.

But we need only know a little about epistemology to see the cracks in objectivity. As we discussed in Chapter 6, the truth that we know is the relative truth, not the absolute. Thus even if the absolute truth is objective, all we know is the relative truth, subjectively mediated by our senses and ability to reason. To say that truth is objective is to make a metaphysical claim we can't prove because our subjective observations don't allow us to know the nature of truth directly. We can at best infer that objectivity is consistent with our subjective experiences of truth, but noth...