Is Substantiality Accidental?

Is substantiality accidental? Can something change from being a substance to being a non-substantial part and back again? Can something change from being fundamental to being non-fundamental or vice versa?

It’s clear that things cannot gain or lose the status of being fundamental, since being grounded by something else is anchored in a thing’s essence, and nothing can change its essence. Could a thing have an essence that makes it dependent in certain circumstances and independent in others? I don’t see how such a disjunctive condition could be an essence – a unified way of being.

However, I have classified proper parts as fundamental things. So, something could change from being a substance to being a proper part of a substance and vice versa without changing its fundamentality status.

Let’s look at the definitions of substantiality that I’ve offered so far:

• S2. A substance is a fundamental particular thing with an essence, whose essence does not entail that the immediate possible existence of members of the kind is partially grounded by the essence of any other thing (except God).
• S3. A substance is a fundamental particular thing whose real definition does not include the predication of a property to anything other than itself and its s-essential parts.
• S4.1 A substance is a fundamental particular thing whose real definition excludes the possibility of its qualifying anything, and which is not a proper part of any fundamental thing.
• S4.2 A substance is a fundamental particular thing whose real definition (i) excludes the possibility of its qualifying anything and (ii) permits the possibility of its not being the proper part of any fundamental particular thing.

Definitions S2 and S4.2 clearly block any change from substantiality to non-substantiality or vice versa, since in both cases they make a thing’s substantiality depend only on its essence.

According to S3, substances have only s-essential parts, and a substance cannot be an s-essential part of anything else. And nothing can lose or gain the status of being an s-essential part.

Definition S4.1 would seem to permit change in substantiality status, since it only requires that a substance not be an actual proper part of another fundamental thing. However, we still have good reason to hold that substances have only s-essential parts, and that no substance can be an s-essential part of another thing.