The purpose of thinking is to let the ideas die instead of us dying – Alfred North Withhead
Evolutionary psychologists regard the ability to think as an adaption. Just like our sense of sight, smell, taste, touch, and hearing have been advantageous to our survival – so has thought.
Buddha had a similar idea, regarding the mind as an equal contributor to our reality as the other five senses. Our thoughts become another way to filter and interpret the world.
I like this interpretation, because it gives meaning to thought.