No concept man forms is valid unless he integrates it without contradiction into the sum of his knowledge

Reasons to agree

1. "A concept" is a belief, or conclusion. The "sum of [one's] knowledge" is all the information, statistics, facts, and arguments that we have rolling around in our head. Valid conclusions take into account real data. Invalid conclusions ignore important data. If we want to believe things that are valid we need to take in accurate data, and ensure that our conclusions don't contradict each other.