I am not sure what do you mean by 'part' and 'whole', but if by 'part' you mean a situation for example, and by 'whole' you mean the universe, well, the situation is very subjective, and you can't really know the whole.

If you are an empiricist you can't be sure about anything, you can't be even sure that your theories are describing what 'is' the world, they are just a way to look at it.

If you are rationalist, you would believe that there are some kind of innate features of your brain, now where those features came from?