2018 has been the year for congratulatory celebrations of Karl Marx' thinking marking the bi-centenary of his birth. But such eulogizing of Marx seems to be out of place in the light of the horrors realized historically by Marx-inspired revolutionaries, e.g., Lenin and Mao. In the light of the seeming connection between Marx' theorizing and the murderous violence and terror carried out in his name, one would wonder how a positive evaluation is morally possible. If Marx' thinking as whole relative to influencing the future is to receive accolades, and if it is true that the thinker Marx is the progenitor of a revolutionary praxis of horror and terror by his followers, then such praise seems to be amiss in a pointedly moral sense. Whatever positive aspects are to be found in Marx's thinking, if the systematic nature of Marx' theorizing generates a principle of violence and terror, then it seems wrong to pile praises upon Marx and Marxism as a systematic whole. Yet fine thinkers did and do praise Marx without any sense of moral onerousness. How is this possible? The answer is simple. Reject any logical continuity between Marx and his adepts. Scholars seek ravenously in the writings of Marx for indications that non-violence is not necessary for a successful overthrow and abolishment of capitalism. (In effect Marx is transformed into a revisionist, as Lenin well knew). The ensuing essay has as its telos to uncover intrinsically and logically the principle directing the use of violence and terror that is intrinsic to Marx's thinking, and this principle is efficacy alone. Materially terror may not be required, but formally it may be used. The essay seeks to give an overview of the evolving thinking of Marx from his-angry poetry of late Romanticism through his Young Hegelianism and his critique of Hegel and others on to his mature thought. The prime problematic experienced by the young poetic Marx was, as he said of his poems, the conflict between "what is" and "what ought to be". Marx quickly abandoned poetic meandering for the power of reason. Nevertheless, the problematic between "is" and "ought" informs his evolving theorizing. Marx was not seeking to understand capitalism ("what is") but to ironize, to annihilate it (for "what ought to be"), and the proletariat was the real material force of such termination. Indeed, Marx' solution assumes form within the terms his incipient materialism and is directed at the problem of enacting revolution. Marx' thinking here is closely examined and its logical influence on Lenin and others is established. Excluding all morality, Marx affirmed the use of force, violence and terror if efficaciously necessary, and such affirmation is event in many of his followers as is shown.