Just for kicks I will propose the following Myers-Briggs type organization of political philosophies. (This is based on a political categorization scheme I saw about 10 years ago. I added the pragmatist vs extremist dimension.) The three dimensions of this categorization scheme are as follows: (The names of the categories are made up since what the heck it is my scheme

, but I think they describe the general relationship between eight different political philosophies. ) .
Pragmatist vs. Extremists
Pragmatist favor working through the system and in particularly respecting democratic principles no matter what the cost. Pragmatists are not always right; they for instance would gladly keep millions of people enslaved in order to preserve the Union.
Extremists have a ‘By all means necessary philosophy’ and may be necessary in the short run but often lead to dictatorships in the long run.
Capitalists vs Unionists
These are the ‘class warriors’. With capitalists on the side of individualism in the use of wealth and the unionists are in favor of protecting the weak from the strong at least in terms of wealth.
Moralists vs Relativists
These are the ‘culture warriors’. Moralists believe that government should at some level encourage or enforce cultural norms such as being against gay marriage and abortion. Relativists believe that government should butt out of all moral affairs. Like all of these categories most people and philosophies are a mixture of both maybe favoring regulation for some moral categories but not for others.
With that overly long introduction let me explain the difference in my oh so humble opinion not only between socialists and communists but of 6 other political categories as a bonus

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Communist (EUM)
Communists favor government control of morals and of economy and do so with a by all means necessary attitude.
Socialists (EUR)
Socialists favor government control of the economy but have an individualists view of morals. The also have a tendency of favoring a ‘by all means necessary philosophy’.
Fascists (ECM)
Fascists favor capitalism or at least allow it but want government control of culture and morals by all means necessary.
Anarchists (ECR)
Anarchist favor no regulation and the complete destruction of government as the only means possible to achieve it.
The pragmatic versions of these four are as follows.
Liberals (PUM)
Liberals believe that government has a role both in morals and in regulating the economy, but critically also believe that it should do so through democratic means.
Progressives (PUR)
Progressives believe that government should regulate the economy but stay out of personal morality. They are the pragmatic/democratic version of the socialists.
Conservatives (PCM)
Conservatives believe that government should fight the culture wars but stay out of the class wars. They are the pragmatic/democratic version of the fascists.
Libertarians (PCR)
Libertarians believe that government should protect all personal freedoms even if those freedoms are used by individuals to hurt themselves and others. They are the pragmatic/democratic version of the anarchists and differ in that the believe in some function of government in some limited cases where one person freedom directly harms another’s freedom and other basic functions of government such as firefighting, etc.
The short summary of all of this is the communists believe in some sort of government enforcement of morality/culture while socialists are more moral relativists. (If you are inclined to argue about communist carrying about morality remember that while the communist Soviet Union favored an atheistic morality it is not the only form of communism.)
The term leftist to my mind is useless since it varies from era to era and place to place but if you force me to chose I would suggest all of the ‘unionists’ philosophies can fairly safely be said to be on the left while all of the ‘capitalists’ philosophies can be fairly safely to be said to be on the right. Both ‘sides’ include ‘positive’ and ‘negative’ points of view.
Any way that is my very non-rigorous point of view.
By the way if someone has a better name for the antithesis of Capitalist, I would appreciate it. I tried Regulationalists but R was already taken

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