Earlier quoted context omitted.
Elon Musk disagrees with that statement. He believes once intelligence gets beyond a certain threshold (which humans have), there are no such things that are beyond understanding. Most people don't know how to write complex math equations, but that doesn't mean they can't understand what mathematics is.
Elon Musk is an engineer, not a philosopher, and I stand to be persuaded, but I find using him to counter Michio Kaku ridiculous.
Being a philosopher is not an extraordinary designation, such that it puts them beyond the mental abilities of someone of Elon's obvious mental aptitude.