Oh mannn, this question is great to talk about.
Hardcore modernists say “Form follows Function”, but I think it really depends on what the function is (and I’m not really all that hardcore… or modern). If we think about a very specific function an object serves, like a ball for golf (I think golf is a ridiculous sport btw) or a screwdriver, then we say that the form is completely defined by the function. The dimples on the ball are there so it can be more aerodynamic. The screwdriver serves one purpose, so it can be reduced down to one design. When we get down to specifics, how to optimize an object’s function, then sure, function defines form.
But say function is secondary. Hmm, teapots! The only things needed for an object to be considered a teapot is a lid, spout, and handle. So really, they can be made into one simple, standard vessel. But I’ve seen some pretty crazy teapots that throw function out the window. Five spouts, three lids, and eight crazy handles and it’s still a teapot; definitely not a very functional one though.
I guess my final answer is that the two are never mutually exclusive. Function doesn’t necessarily define form but it guides it and offers parameters. And if it were only a “Yes or No” question I’d saayy…Yes… Maybe.
I think I’ll be thinking about this all day, thanks for the question~