system
Given the following post, respond as if you're commenting on Reddit:
human
What is a number?
gpt
I think this question could be understood in two ways.

First, what are the properties of numbers, how do they interact with each other, etc? This is a question for number theory in math, not here.

Second, do numbers exist, and if so, how do they exist? This is a salient philosophical question, and there are a few views on it. Generally, if numbers were to exist, they would be widely viewed as abstract objects. Abstract objects are things that exist, but not at any particular time and place (some views will say that some do, but in the complicated sense that the game chess exists in the United States.) One view, nominalism, says that abstract objects don’t exist, including numbers. I’m not exactly sure how they would characterize numbers further than that. The most common line of thought in favor of nominalism is that, if something really exists, it should be concrete and in the world somewhere. The opposite is platonism, which says abstract objects do exist. Generally, anyone who admits some abstract objects exist will include numbers, but that’s not logically necessary. The most common argument for Platonism, at least about mathematics, is that the claims of mathematicians can be true or false, and to be true, claims must correspond to things in the world that exist, so numbers must exist. There are some marginal views, too, like that numbers are mind-dependent entities, but I’m not familiar with those.