Thales is the first known person to use natural explanations, rather than supernatural explanations, for natural phenomena in the world.
Other Greek thinkers followed Thales example, developing natural philosophy, the precursor to science.
This revolutionary approach to philosophical questions developed by Thales, was based on the concept that the essence of all matter, was water. Thales observed the natural world and noticed, among other observations that, all life depends on water – remove the water from a plant and it dies. Or, deprive animals of water and they die.
Thales' statement, "The most difficult thing in life is to know yourself,” encouraged the exploration of fundamental questions of existence.
And this foundation, led to Western philosophy focusing on questions like the purpose of life, death, and existence, using a more analytical and rational lens.