When you talk about "the goal", then the natural thing to ask is "who's goal are you talking about?"
If you're asking what motivates *scientists* to do what they do, then you need to ask the actual scientists, and be prepared for them to all have their own indivisual answers. But it seems more like you're asking what "The Goal of Science(TM)" is, in some absolute sense... which, to be a meaningful question at all, requires there to be some Absolute Person(TM) who has this Goal(TM) to which you refer... which naturally means you're going to be talking at cross purposes to half your readers, whom you already know are atheists, when you ask the question.
Re: Rounding off--a provisionally final attempt to explain myself
If you're asking what motivates *scientists* to do what they do, then you need to ask the actual scientists, and be prepared for them to all have their own indivisual answers. But it seems more like you're asking what "The Goal of Science(TM)" is, in some absolute sense... which, to be a meaningful question at all, requires there to be some Absolute Person(TM) who has this Goal(TM) to which you refer... which naturally means you're going to be talking at cross purposes to half your readers, whom you already know are atheists, when you ask the question.