In Plato’s Phaedo, Plato talks about believing in how things grow, or how they come to be. When he states that he doesn’t even know if 1+1=2 I became rather confused. What does math have to do with Philosophy? 1+1=2 because that is a mathematical principle that follows rules. 1+1 will always equal 2. It is not our senses that are making 1+1=2, it in not our brain that is making 1+1=2, it is principles and law of mathematics that makes one object plus another object equal 2 objects.
It makes sense when Plato questions how a man grows: flesh on top of flesh; the multiplication of flesh. There are other factors that could make a man bigger other than just the multiplication of flesh. It could be fat that is making one man bigger. It could be the thickness of his bones or his height. There are many variables that make a man bigger than another but when it comes down to it a the man that is bigger is mathematically larger. measurements can proven he is, which is why we rely on mathematics so much in this world. Because is there is so much room for interpretation or question, there needs to be a principle that humans can rely on to compare things: measurements and numbers is one of those things.
Math is reliable because it doesn’t rely on sense that can deceive you, it doesn’t come from circumstance or opinion, it comes from rules, which is basically what math is: following sets of rules with certain numbers to get a precise outcome that cannot be argued. So my point is if math does not rely on the things that Plato says deceive us, why would he doubt it?