[jjk166]

You won't ever have the exact same set of initial conditions in any experiment. You drop two balls from the tower of pisa and do it again you have different air conditions, the planet has moved, the tower may have leaned slightly more, etc. You either control for these variables or assume they don't matter. The value of science is that even if you drop two balls on the moon, you're still going to get the same result after controlling for differences - the results are broadly applicable. It's exactly the same in the social sciences. If you're looking at something real, it will show up consistently in repeated experiments with proper controls despite variation in irrelevant initial conditions. The phenomena that social sciences try to understand may have many more variables, but there's nothing inherently special about humanity that makes us impossible to describe.

[pepinator]

I'm not saying humanity is impossible to describe (on the contrary!). your physics example is too different to what happens in social sciences, it's not a good analogy. you can largely control the conditions under which you throw the balls, while if you're, for instance, studying the recent socio political events in the USA, things are given and then you need to rely on similar past event to understand current ones. even in fields like psychology it's too difficult to even measure initial conditions and outputs. that's why you rely on qualitative analysis.