Babbage difference engine On the left is the first mechanical tool that seemed to “think”: the difference engine devised by the British mathematician Charles Babbage. It could compute solutions to complex mathematical formulas. The power of machines such as the difference engine inspired students of the brain to propose that the brain could be understood as a mechanical device—a thinking machine in your head. On the right is the biological tool that Babbage used to invent the difference engine; Babbage’s own brain is preserved in a science museum in London.