Arguments fall into two categories. 1) property rights and 2) increased utility

As for #1 if ideas are property whoever's dad created fire should still have the patent and we all owe a lot of money. But ideas aren't property. Property exists to divy up scarce resources and ideas are not scarce. If you make this argument for patents the logical conclusion is that patents should be eternal, the first person to come up with an idea should own it forever.

So that leaves the utilitarian argument for patents but you won't see anyone actually cite any data in favor of patents. The idea that filing a patent disseminates knowledge is a farce. In the US 12% of R&D budgets go to paying off patent trolls. And that number has been rising.