My tendency has long been to use 'reification' and 'hypostatization' interchangeably. But a remark by E. J. Lowe has caused me to see the error of my ways. He writes, "Reification is not the same as hypostatisation, but is merely the acknowledgement of some putative entity's real existence." ("Essence and Ontology," in Novak et al. eds, Metaphysics: Aristotelian, Analytic, Scholastic, Ontos Verlag, 2012, p. 95) I agree with the first half of Lowe's sentence, but not the second.
Lowe's is a good distinction and I take it on board. I will explain it in my own way. Something can be real without being a substance, without being an entity logically capable of independent existence. An accident, for example, is real but is not a substance. 'Real' from L. res, rei. Same goes for the form of a hylomorphic compound. A statue is a substance but its form, though real, is not. The smile on a face and the bulge in a carpet are both real but incapable of independent existence. So reification is not the same as hypostatization. To consider or treat x as real is not thereby to consider or treat x as a substance.
Lowe seems to ignore that 'reification' and 'hypostatization' name logico-philosophical fallacies, where a fallacy is a typical mistake in reasoning, one that occurs often enough and is seductive enough to be given a label. On this point I diverge from him. For me, reification is the illict imputation of ontological status to something that does not have such status. For example, to treat 'nothing' as a name for something is to reify nothing. If I say that nothing is in the drawer I am not naming something that is in the drawer. Nothing is precisely no thing. As I see it, reification is not acknowledgment of real existence, but an illict imputation of real existence to something that lacks it. I do not reify the bulge in a carpet when I acknowledge its reality.
Or consider the internal relation being the same color as. If two balls are (the same shade of) red, then they stand in this relation to each other. But this relation is an "ontological free lunch" not "an addition to being" to borrow some phaseology from David Armstrong. Internal relations have no ontological status. They reduce to their monadic foundations. The putatively relational fact Rab reduces to the conjunction of two monadic facts: Fa & Fb. To bring it about that two balls are the same color as each other it suffices that I paint them both red (or blue, etc.) I needn't do anything else. If this is right, then to treat internal relations as real is to commit the fallacy of reification. Presumably someone who reifies internal relations will not be tempted to hypostatize them.
To treat external relations as real, however, is not to reify them. On my use of terms, one cannot reify what is already real, any more than one can politicize what is already political. To bring it about that two red balls are two feet from each other, it does not suffice that I create two red balls: I must place them two feet from each other. The relation of being two feet from is therefore real, though presumably not a substance.
To hypostatize is is to treat as a substance what is not a substance. So the relation I just mentioned would be hypostatized were one to consider it as an entity capable of existing even if it didn't relate anything. Liberals who blame society for crime are often guilty of the fallacy of hypostatization. Society, though real, is not a substance, let alone an agent to which blame can be imputed.
If I am right then this is mistaken:
First, I have given good reasons for distinguishing the two terms. Second, the mistake of treating what is abstract as material is not the same as reification or hypostatization. For example, if someone were to regard the null set as a material thing, he would be making a mistake, but he would not be reifying or hypostatizing the the null set unless there were no null set.
Or consider the proposition expressed by 'Snow is white' and 'Schnee ist weiss.' This proposition is an abstact object. If one were to regardit as a material thing one would be making a mistake, but one would not be reifying it because it is already real. Nor would one be hypostatizing it since (arguably) it exists independently.