unsubstitutable

It is only at the resurrection that the identity of Jesus becomes fully manifest, but is it not as a mythological figure, but the human Jesus, and ‘regarded as an unsubstitutable individual in his own right’, and in this sense is ‘most fully historical’.

What is Human Wisdom?: An Interrogation of Posthuman Futures in Transhuman Evolutionary Discourse By Celia Deane-Drummond William Harryman 2009

Those costs are completely alien to the wind and solar industry, unless you can find me a rare “unsubstitutable” resource that only exists in an enemy nation.

Coyote Blog » Blog Archive » Oil at $140 is Still a Modern Miracle 2008

Lumping together (to cite just a few of scores of possible examples) highly substitutable but relatively limited resources of liquid crude oil with unsubstitutable but immense deposits of sedimentary phosphate rocks, or short-lived atmospheric gases with long-lived radio - active wastes, struck me as extraordinarily meaningless.

the Foresight Institute 2009