Complex sentence: Jurisch understands himself as a gentlemen philosopher in the tradition of the eighteenth and nineteenth century, who carried out science in their leisure time, and by the understanding that science is an art but no business.
Split into simpler sentences: Jurisch understands himself as a gentlemen philosopher in the tradition of the eighteenth and nineteenth century. Gentlemen philosopers are doing science in their leisure time, and by the understanding that science is an art but no business.