The mathematical answer is that if your interest rate is lower than the expected returns of some kind of portfolio you have, than you'll make more money investing.
But I like to bring up what Morgan Housel, author of the book The Psychology of Money, said on paying down his mortgage:
> It just increased our independence, even if it made no sense on paper. So that's another element of debt that I think goes misunderstood. And a lot of that for both of those points is this idea that people don't make financial decisions on a spreadsheet. They don't make them in Excel. They make financial decisions at the dinner table. That's where they're talking about their goals and their own different personalities and their own unique fears and their own unique skills and whatnot. So that's why I kind of push people to say like, it's okay to make financial decisions that don't make any sense on paper if they work for you, if they check the boxes of your psychology and your goals that makes sense for you. And for me, extreme aversion, what looks like an irrational aversion today, and I would say is an irrational aversion to debt, is what works for me and what makes me happy, so that's why I've done it.