A Shot at Metaphysical Terms
Metaphysics can be concerned with things so basic that it’s hard to understand, and the language only makes it harder. The hope here is to provide a quick guide to help with key terms: “essence,” “substance,” and “form.”
Different thinkers seem to use these terms in different ways, and someone like Aristotle strikes me as using them like similes one moment, only to use them like they are incredibly distinct the next. A true scholar of Aristotle could easily perceive distinctions I cannot, but my hope is to still provide a general guide. If it is useless or too incomplete to be of value, please disregard it.
So, for my take on the terms:
Essence is what makes a thing that particular thing. In other words, essence is what makes “that chair.”
Substance is what makes a thing a general thing. In other words, substance is what makes “a chair.”
Form is what makes the idea of a thing, without which the thing would not be intelligible. In other words, form is what makes “that idea of a/that chair.
These terms can be unified in one phenomenon and distinct in another, so there are times when the categories overlap, making them seem identical. Something with essence also has substance and form, and since everything is a particular thing in the world, everything in the world entails all three categories.
A thought experiment that might help:
Imagine I am cloned. My clone will have my substance and form, but it will not have my essence. Now imagine my clone tells you that it is a clone; suddenly, the clone will have my substance, but not my form. Thus, my clone never has my essence, has my form contingently, and always has my substance.
And there we go! I hope this helps us get a grip on some famously confusing terms. That said, the brilliant Thomas Jockin pointed out a need for distinctions between “particular” and “individuated,” and also brought to my attention the useful scholastic term haecceity, which I encourage readers to investigate. Distinctions should also be made between “primary substances” and “secondary substances,” and in some metaphysical schemas, my clone and I share the same essence while being different primary substances. In my work, “essence” and “primary substance” are used similarly, and that could easily be a mistake. Still, I think the distinctions I laid out are useful (at least somewhat) even if incomplete, and perhaps I should just use the letters A, B, and C to signify the distinctions versus risk using metaphysically rich concepts wrongly. If I have made mistakes, please extend me your forgiveness.