The left–right political spectrum is a diagram intended to categorize political ideologies in 3 distinct categories: left wing, right wing and centrist. The model has received criticism for being idealist, unscientific, subjective, and for ignoring historical materialism and class struggle.
There are successors or variations to the left-right spectrum, one of the most famous successors being the political compass. Variations include the Horseshoe Theory and the Fish hook theory.
The methodology is derived from the time of the French Revolution of 1789, wherein the newly formed National Constituent Assembly had overtime been divided from left to right. With the persons in opposition to the monarchy sitting to the left, whilst the inverse sitting on the right. This evolved with the establishment and replacement of the National Assembly with the Legislative assembly in 1791. With new members and principles, however, the fundamental seating of ideological motives was maintained with the so-called “innovators” on the left, the “moderates” in the middle, and the “conservatives” on the right.
The model is split into 3 categories (sometimes 2), the left wing, the right wing and the centrists. There can be also prefixes adjoined to the parts of the spectrum as 'far-left' or 'center-right' (not to be confused with centrist), which specify the location within the political spectrum. It is a visible one dimensional line going from left to right.
The Left Wing broadly describes the progressive of the status quo in a given society, from Marxism-Leninism to social democracy ideologically wise, or the support of specific policies: like the support of LGBT rights in the USA.
No to be confused with apolitical and moderate, they are typically people who support (and somewhat oppose) both stances, sometimes rejecting one idea of the part over another or choosing neither. Principally, however, in analysis, these persons uphold the status quo, and thereby overlap with the Right wing.
The Horseshoe Theory is an adaptation of the Left-Right Spectrum, where the furthest left and the furthest right points are brought closer together in the form of a 'horseshoe' shape, to state that the far-left is similar or identical to the far-right. This is despite the fact that historical materialism refutes this, as the far-left are often anti-fascist and fought nations such as Nazi Germany.
Fish Hook Theory
The Fish Hook Theory is an adaptation of the Left-Right Spectrum where the far-right is shaped towards the center, in the shape of a 'hook', to state that old sayings such as 'Scratch a liberal, a fascist bleeds'. This is more accurate, however, this falls apart due to subjectivity and its unscientific nature.
The Left-Right Spectrum changes depending on which region you live in. In the United States, Social Democrats are considered 'far-left' and Liberals are considered 'Left-Wing' whilst Conservatives are considered 'Center-Right'.
In the case of the UK for example, Liberals are considered 'Center-Right', and Social Democracies are considered 'center-left' whilst socialists are considered 'far-left'.
The Left-Right Spectrum is criticised for not being scientific, as you cannot draw conclusions due to its subjectivity. There is also no consensus on how to measure the ideologies based on a certain factor, note that the left-right spectrum relies on one value more often than not to be considered scientific.
It is an absolutist model, putting ideologies in a vacuum, as some models include "Monarchism" as a 'far-right' ideology, despite monarchism being obsolete for decades.