Where can I read about objections to the validity of a question such as "the purpose of life" where the question baselessly presupposes that life HAS a purpose. And more broadly, even if it claimed that EVERYTHING has a purpose, how can such a claim be justified? It seems that many metaphysical questions suffer from this lack of validity due to unfounded presuppositions or assertions. Where can I read about this as applied to philosophical questions in general?
I recommend the essays in Part Three ("Questioning the Question") of E.D. Klemke's collection The Meaning of Life (Second Edition). If I may also mention my own short article on one aspect of this topic, you can find it at this link . The literature on whether philosophical questions in general rest on false presuppositions is enormous. You might start with this SEP article (especially section 4.1). There's also a growing literature on whether metaphysics in particular (and ontology more particularly) concerns mostly pseudo-questions; see, for example, this collection .