Thoughts are to life, what life is to matter, an increase in complexity.
Much in the way the homo sapien body consists of millions of systems within organs and cells, the large brain we have unlocked our greatest advantage, abstract thought. Animals can hunt, but we can hunt with far greater complexity, and yet for thousands of years our progress was slow and uneven around the globe. The big "boom" periods came with society in agriculture, industrialization, and now the modern communication era. We use ratcheting knowledge to build and communication through language to rapidly increase our capacity.
It may seem circular in nature, but we consider these questions because of our nature as humans. It is possible an alien life somewhere in the galaxy exists and simply ignores notions of philosophy and meaning. We won't know until we have comparable complex sentient species to contrast ourselves against.
