The US Constitution exists materially as a piece of parchment paper impregnated with ink, and as such is clearly not alive in any biological sense. However, the assertion of a “living” Constitution is a euphemism suggesting that the document should be reinterpreted at-will in a way that suits society at a given time and promotes “Progress.”
In interpreting the Constitution not according to its original intent (originalism), nor by its plain language as understood at the time it was written (textualism), but rather according to the whims of those charged with the task, the meaning of the document becomes unmoored from any principles that could be said to be eternal - that of an ethic - and endorses the views of Progressive Historicism: History as a spirit that must necessarily progress towards an end point of the perfected state (utopia). It is this desired, utopian end for Progressives that justifies the denial of the eternal truths put to paper by the American founders in the Constitution: natural law, natural rights, and God.
This project of “living Constitution[alism]” has roots to the early 20th century and has been undertaken from its beginning specifically, and explicitly to remove the Constitutional checks on governmental power that would have blocked the creation of the bureaucracy of “experts” sought by Progressives to deliver us into the ‘perfected state.’ This project was championed by Woodrow Wilson, and Franklin Delano Roosevelt among others - as they praised Mussolini - in a quasi-religious undertaking to bring about the “end of history,” or a time when the suffering of mankind would be brought to an end through living in perfect harmony with the perfected State as a collective.
Fundamental to the Progressive view of a “living Constitution” is that rights are neither derived from God, nor individual in nature, but rather granted by the state, and collective in nature. This is the same conceptualization of “rights” held by Communists, and Fascists, and strongly lends towards totalitarianism, and catastrophe. This formed the basis for the conceptualization of “human rights,” which, as a phrase, is designed to negate “natural rights” along dialectical lines of thesis, antithesis, and synthesis, and subvert our understanding of liberty as held by American tradition. The synthesis of these terms over the years has led, purposefully, to much confusion about the nature of rights, and has largely supplanted concepts of inherent rights with those of might-makes-right Hobbesian power struggles, amorality, nihilism, relativism, and victimhood culture of wound collecting.
The founders had a coherent worldview, and moral framework from which they derived the eternal truths of individual, God-given rights. This followed in the Anglo-Saxon traditions of England from the Magna Carta onward as the understanding of sovereignty shifted from the Monarch to the individual, which in turn gave rise to the concept that a ruler requires the “consent of the governed” to be legitimate, as he acts as an upward accumulator of sovereignty passed willingly from the individual with which to carry out limited functions of legitimate authority on their behalf. These truths were put to paper quite plainly for all to read and understand; so, as you see, the Constitution is, properly interpreted, frozen in meaning to the time, and the manner of our founding, in no way whatsoever “living,” and to argue otherwise is done from a position of bad faith intended to deprive us of our liberty, our happiness, our freedom, and, ultimately, our lives.