Property inheritance

There seems to be such a thing as property inheritance, where x inherits a property F from y which has F in a non-derivative way. Here are some examples of this phenomenon on various theories:

1. I inherit mass from my molecules.

2. A person inherits some of their thoughts from the animal that constitutes the person.

3. A four-dimensional whole inherits its temporary properties from its temporal parts.

These are all cases of upward inheritance: a thing inheriting a property from parts or constituent. There can, however, be downward inheritance.

4. When a whole has the property of belonging to you, so do its parts, and often the parts inherit the property of being owned from the whole, though not always (you can buy a famous chess set piece by piece).

There may also be cases of sideways inheritance.

5. A layperson possesses the concept of a quark by inheritance from an expert to whom they defer with respect to the concept.

There seems to be some kind of a logical connection between property inheritance and property grounding, but the two concepts are not the same, since x’s possession of a property can be grounded in y’s possession of a different property—say, a president’s being elected is grounded in voters’ electing—while inheritance is always of the same property.

It is tempting to say:

6. An object x inherits a property F from an object y if and only if x’s having F is grounded in y’s having the same property F.

That’s not quite right. For if p grounds q, then p entails q. But this bundle of molecules’ having mass may not not entail my having mass, since it might be a contingent feature of the bundle that they are my molecules, so there is a possible world where the bundle exists and has mass, but I don’t (if only because I don’t exist). It seems that what we need in (6) is something weaker than grounding. But partial grounding seems too weak to plug into an account of property inheritance. Consider my property of knowing something. One of my pieces of knowledge is that you know something. So my knowing something is partially grounded in your knowing something, but I do not think that this counts as property inheritance. (Suppose one bites the bullet and says that my knowing something is inherited from you. Then, oddly, I have the property of knowing something both by inheritance and not by inheritance—inherited and non-inherited property possession are now compatible. I don’t know if that’s right, but at least it’s odd.)

I think we can at least say:

7. An object x inherits a property F from an object y only if x’s having F is grounded in y’s having the same property F.

But I don’t know how to turn this into a necessary and sufficient condition.