The phrase "a radical error" is correct and usable in written English.
It can be used to describe a significant or fundamental mistake in reasoning, judgment, or action.
Example: "The analysis presented a radical error in its assumptions, leading to flawed conclusions."
Alternatives: "a fundamental mistake" or "a severe miscalculation."
"There is a radical error, I think, in the usual mode of constructing a story," Poe writes in "The Philosophy of Composition," a great, mad essay from which young scribblers may still profit.
But Gnosticism, even in its pre-scientific forms, is a radical error.
This is a consequence of the view which Davidson embraced (see Davidson 1974); but one might also reasonably think that radical disagreement, as well as radical error, are possible, and hence that any theory, like Davidson's, which implies that they are impossible must be mistaken (see Chapter 13 of Soames (2003) for discussion).
And thus, Naess concludes, the program of a pure logic as a system of apodictic knowledge is "to be dismissed … As soon as a science is said to be science of or about something, there is a radical risk of error …" (Naess 1954, 73).
A typing error on a radical newsletter her flatmate received in the post gave her the idea.
"If you said you were sorry you were a radical and had seen the errors of your ways, you were let off," Mr. Polonsky said in an interview in 1968.
Their success was due primarily to their innovative research methods, which marked a radical departure from the trial-and-error approach taken by previous pharmacologists.
It made bad errors and it required a radical reform.
And earlier this year the University of Irvine Medical Center unveiled a radical scheme that is helping to reduce the number of deaths caused by medical error.
More than two amino acid intraspecific changes could represent a radical change [142] at highly conserved COI gene and as they are likely caused by sequencing error [119].
I have a radical dislike of radicals".
