Simplify the following text for a Grade 8 native English-speaking person.
Original: The Dutch professor Francois de la Boe Sylvius , a follower of Descartes , believed that all disease was the outcome of chemical processes , and that acidic lymph fluid was the cause of cancer .
Simplified: The Dutch professor Francois de la Boe Sylvius believed that all disease was the outcome of chemical processes . He believed that acidic lymph fluid was the cause of cancer .