A while back I posted this question on Aeon Ideas: 'Is there anything that we can have absolute certainty about?' Tushant Jha posted a response that is so elegant that I thought it worth sharing here too:
“Let us say that we are certain of proposition X. Then we are certain of the proposition “There exists a proposition we are certain about”. And also be certain about the proposition “There are at least two propositions we are certain about”. and Ad Infinitum.
However, let us say, that there is nothing we are certain about. Then, not strangely, we cannot even be certain about this assumption that “nothing is known certainly”. This is indeed getting caught up in a strange loop.
Thus, without answering the question, one could really remark at the philosophical beauty of this query, of which on one side lies an unending staircase of infinite regress, and on other a self-referential strange loop. Truly remarkable.”