Descartes is commonly regarded as a modern thinker who first provided philosophical frameworks of natural sciences. In his work Meditations on First Philosophy, he attempted to arrive at an original set of ideologies which can be accepted as true by anyone without doubts. He then employed methodological skepticism wherein he doubted any idea that appears to be doubtful just to create a solid foundation for authentic knowledge.
In the system of Descartes, knowledge can take the forms of ideas while philosophical investigation contemplates these ideas.