The math controversy that, they say, led to a mental breakdown

In an essay called “The Root of Infinity: It’s Surreal!“, the ThatsMath blog writes about a dark side to the power of numbers. The Cantor mentioned here is George Cantor [pictured here], who pretty much created the branch of mathematics now called number theory:

… But the extended system was hugely controversial, and for good reasons. For example, Cantor found that . His system was not commutative under addition. In fact, . We might be tempted to subtract  from each side, but this would yield the nonsensical result . The controversy was a factor in Cantor’s mental breakdown and ultimate suicide.