If I may, I do accept the existence of a realm of immateriality. One problem, as I see it, has been applying immaterial truths (i.e., beliefs) to the governance of society. (In the absence of a universally held, pertinent belief) that can only result in a belief held by some being imposed on all. People who are forced to live according to beliefs they do not hold experience that as 'injustice'.

Only materiality offers the possibility for an approach to governing society that has the commonality justice requires. Understanding that Marx rejected any idea that justice is a 'real thing', locating the idea of justice in materiality merges the two realms of existence.

Warren J. Samuels all but defined "social power" as the ability to effect choices. It is the case that humans, as material beings, have no choice but to effect choices. That makes choosing integral to being human. So justice is people respecting the capacity of other people to choose for themselves--beginning with whether/how/to what extent to be involved whenever any choice is being effected.

I have developed that into an approach to governing society justly that can replace 'old' Liberalism, based as it has been on believing in liberty and equality as the 'twin pillars of justice' for a just society. This approach does maximize liberty--as a product of justice--but it makes equality an unnecessary complication: all that matters for justice is that the beings involved are humans.

if curious: "A New Liberalism" (here in Medium, but--for the benefit of any 'guest readers'--not behind the paywall)