Consider Newton. He pursued physical theories, alchemy and theological studies with similar amount scholarship and zest. His physical theories obtained popularity due to its utility. And his theological and alchemical studies didn't give the world any material benefits and so the world calls those areas of his output "random speculations". But at the core of all these three attempts is a probing, speculative mind. That is my definition of philosophy, that there is an intensely curious mind, which will pour forth effort in understanding the world (including oneself). Newton's subject area was called "Natural Philosophy" for nothing. There are less "successful" philosophers and streams of philosophy, of course.