Mark Zbikowski told me a story from the early Windows NT days.
He found a race condition in the file system code and went to see the lead developer for the I/O subsystem.
"There are no bugs in the I/O Manager," the developer proclaimed.
Mark walked through the scenario to demonstrate the problem.
The lead developer went to his editor and typed furiously for two or three minutes, ending with a theatrical punch of the Enter key.
And he turned to Mark and proclaimed, "There are no bugs in the I/O Manager."