Lawrence H. Summers’s six-part Masterclass on Making Complex Decisions is available on Big Think+.

Lawrence Summers: One has to make a core decision in how to approach the world. Is there a reality, which we struggle to apprehend better and better? That would be my view. Or do we each have our own reality, which is equally valid and to which we are equally entitled? And philosophers debate that kind of question and at some level it’s a profound philosophical issue that is certainly beyond my competence and probably isn’t relevant for practical purposes.

But for practical purposes, for decision makers, if you’re deciding whether to introduce a new product, you’re deciding whether to create a new division of your company, you’re deciding what the right person to hire—who the right person to hire for a given role is, for those kinds of decisions, it’s important to understand what is true and to understand how the world works so that you can judge the consequences of alternative courses of action as accurately as possible.

And what’s essential is not to confuse what one would like to be true with what, in fact, is true.