Retortion

From Logic

A defense through Retortion occurs whenever an argument relies upon the very principle it seeks to overturn.

Those who invalidate reason ought seriously to consider whether they argue against reason with or without reason. If with reason, then they establish the principle that they are laboring to dethrone: but if they argue without reason (which, in order to be consistent with themselves they must do), they are out of reach of rational conviction, nor do they deserve a rational argument. - Ethan Allen, Revolutionary War hero

References

• Copi, I. M, Cohen, C., (2001), "Introduction to Logic", 11th Edition.