A word ending in “ism” denotes an ideological or doctrinal trend deriving from a philosophy. Thus we have positivism, socialism, republicanism, spiritualism, idealism, materialism, etc. None of these words, however, denotes the philosophy itself.
In fact, it might be directly opposed to it. Marx and Kierkegaard both tried to prevent their thinking from being reduced to an ideological mechanism. But they could not stop their successors from freezing their living thought into one (or many) systems, and in this way an ideology arose. Even Sartre accepts the term existentialism without seeing how it perverts what he is saying.
The moment the mutation takes place from existential thinking to existentialism, a living stream is transformed into a more or less regulated and stagnant irrigation channel, and as the thought moves further and further away from the source it becomes banal and familiar.
The suffix “ism” injects something new into a well-marked and well-defined complex. As originality is eliminated and replaced by commonplaces, the life and thought lose their radical and coherent character. The well-defined complex is now vague and fluid. Passages are dug out in all directions. From the point of departure various possibilities open up for exploitation, and they are in fact utilized. There thus comes into being a curious complex formed of many tendencies, often contradictory but all covered by the relevant “ism.” In a final loosening of the original knot of life and thought, which are generally united in the creator and his immediate disciples, the “ism” sometimes takes the form of a practical sociological trend, a type of organization or mass movement, such as socialism, communism, royalism, or republicanism.
At this point there is an even greater distance between the rock of the first life and thought and the sandy wastes that now engulf it. Marxism and what has been derived from it for a whole century have nothing in common. It is the same whenever an “ism” is made in the name of some creator, such as Thomism, Lutheranism, or Rousseauism. It seems that in each case the deviation and subversion mentioned are typical of the Western world.
Jacques Ellul
And of course Christian-ism too as the original Western power-and-control-seeking meme, with its self-appointed "great commission" to convert all human beings to the one-true-faith.
Never mind that Jesus, who was never ever in any sense a Christian, nor did he create the power-and-control-seeking institutional religion about him, every minute fraction of which was created by people (most men of course) who never ever met Jesus up close in a living-breathing-feeling human form, and thus never participated his teaching demonstration while he was alive nor did they receive his very human personal guidance in how to incarnate the Spirit-Breathing Way that he taught.
And of course the "resurrection" never occurred, could not have occurred.
I would appreciate hearing a critique of Thomism.