Personal Knowledge is a treatise on the nature and justification of scientific knowledge. Ultimately, it is designed to show that complete objectivity in the exact sciences is delusion and, ‘in fact’, a false ideal with crippling consequences. We inevitably see the universe from a personal point of view and this, in turn, is inevitably shaped by our human interactions. Attempts to eliminate the personal perspective from our view of the world lead to absurdity. ‘Personal knowledge’ inescapably involves the epistemic standpoint of the investigator. It is an intellectual commitment and, however hazardous, ultimately tends to liberate. To count as knowledge, it must be possible for affirmations to be false. However, items of knowledge are not arbitrary, but rather responsible and intelligent commitments based on the investigator’s epistemic standpoint, skills and human interactions.