Rene Descartes is attributed with starting modern philosophy. With his Meditations he asked questions of methodical doubt, questioning whether he could really know any of his sense data. In his methodical doubt, he tried to doubt everything, including whether he could trust any of his senses. When you do that, all you are left with is your mind. So ever since Descartes, philosophers have been discussing this issue of mind & body, how they are separate and how they relate to each other. For many, the discussion ends in total skepticism, with people saying that we can’t know anything.
But Descartes never really believed it. At the very end of Meditations, he states that it is foolish to doubt your sense impressions, and no sane person ever really did. He states that his little exercise was only to show that the existence of God is more sure than anything else we know. So why are philosophers still doubting sense impressions? They cannot truly live life on a daily basis like they doubt their senses, and there is no solid reason to doubt them.