“The figurative use of the term grows out of the idea that radical change means change at the very deepest levels, change at the roots of a system. The radical mind is one that wants to find the roots and then to see them as they are, to see what they look like in the absence of ideological appurtenances.”
https://theanarchistlibrary.org/library/david-s-d-amato-toward-an-explanation-of-the-radical