What is "the speed of thought?" If he's referring to how fast can a person think (i.e. how rapidly can a mind create different thoughts or concepts), then that is a rate, NOT a speed. If he is referring to how rapidly can thoughts, information, ideas, etc. be communicated from one mind to another by any process, that's still limited to less than the speed of light. (I cannot inform my friend on Sirius (which is 9 light years away) of my breakthrough in physics for another 9 years. That's how long the signal sent out today will take to get there.) "The speed of thought" is a meaningless (but glib sounding!) concept in this sentence. This is a classic example of Dirac's complaint about something being so bad "it's not even wrong."