Horseshoe theory

In popular discourse, the horseshoe theory asserts that advocates of far-left and the far-right politics, rather than being at opposite and opposing ends of a linear continuum of the political spectrum, closely resemble each other, analogous to the way that the opposite ends of a horseshoe are close together. The theory is attributed to the French philosopher and writer of fiction and poetry Jean-Pierre Faye in his 2002 book Le Siècle des idéologies ("The Century of Ideologies").

Several political scientists, psychologists, and sociologists have criticized the horseshoe theory. Proponents point to a number of perceived similarities between extremes and allege that both tend to support authoritarianism or totalitarianism; political scientists do not appear to support this notion, and instances of peer-reviewed research on the subject are scarce. Existing studies and comprehensive reviews often find only limited support and only under certain conditions; they generally contradict the theory's central premises.