Karl Marx: The same men who establish their social relations in conformity with the material productivity, produce also principles, ideas, and categories, in conformity with their social relations. Thus the ideas, these categories, are as little eternal as the relations they express. They are historical and transitory products. There is a continual movement of growth in productive forces, of destruction in social relations, of formation in ideas; the only immutable thing is the abstraction of movement — mors immortalis. ( From Lucretius's poem On The Nature of Things: "mortalem vitam mars immortalis ademit" ("moral life has been usurped by death the immortal").) https://wordsmith.social/protestation/quotes#quote4140