(1) Every agent acts for some end.
a. Substances that lack agency also “act” for some end as they bring about effects.
(2) When an agent can act for a range of ends, there is no reason that the agent should pick one end over another.
a. In substances that lack agency, while the substance does not have the ability to “pick” one end over anther, it is possible that any number of ends could be sought—and there is no reason one end ought to be preferable to another.
(3) In our experience, substances have characteristic functions and bring about characteristic ends.
(4) As efficient causality refers to the capacity to bring about some effect, so final causality refers to the determination that is made to bring about certain effects instead of others
a. In substances that lack agency, this determination to bring about certain effects is built into their very nature.
(5) The internal directedness of a substance to its characteristic ends is an expression of its essence/nature in the context of efficient causality.
a. In other words, since the essence makes a substance to be a certain kind of thing, the characteristic effects that a substance brings about originate from its essence.
Now, you might ask why this is relevant to an intro course in clinical ethics. I think that thinking about "characteristic functions" and "natural tendencies" is an easy bridge into a deeper discussion of what those concepts actually mean. And "function" and "tendency" are a large part of medical science--practically all of biology utilizes this terminology without much consideration of what makes a function a function, or a tendency a tendency.
When a doctor tells you that your heart is not working properly, he must have a reference for what a properly-working heart looks like. Likewise, when a doctor prescribes a certain medication, he knows what the medicine tends to do for patients. Furthermore, the pharmacist knows about the tendencies of the ingredients of a certain drug, and he knows how those ingredients function together.
Now, there are basically two approaches one can take at this point: either we can know something about the nature/essence of those drug ingredients, or the heart itself, or we cannot know the nature/essence of things in themselves. David Hume, and many scientists today, take the latter approach, while Aristotle, Aquinas, and others take the former. Obviously, I opt for the former approach. Here is why.
IF we are a Humean, then hearts tend to pump blood. That is all. Every heart we have come across does, in fact, pump blood, but we don't know what a heart really is. Hearts simply pump blood in our experience.
This is a really unsatisfying answer. However, the Humean will look to the history of science and point out all the failures and misunderstandings up to this point, and he will say we cannot know, for certain, that we are right about hearts pumping blood.
Now, the Humean has a point about human history--we tend to discover that our ancestors were wrong about things (see flat-earthers). But is this really the alternative?
I think not. Aristotle and Aquinas (A-T) argue that all substances have natures, or essences, which make them to be what they are. These essences are formally responsible for the properties, characteristics, tendencies, powers, etc. of a given substance. When we say that a heart pumps blood, we mean that, given our empirical observations (and historical record of observations), it is in the nature of hearts to pump blood. The heart itself is perfectly suited and designed to pump blood, and it does not have a function outside of a chest.
Where this train of thought gets really interesting is when we think about hearts at the molecular level/microscopic level. All organisms and all parts of individual organisms start to look strikingly similar--so why do the macroscopic organs, and individual organisms, have such diversity when the base layer is either the same or very close to the same? Because macroscopic organisms, or individual substances, are ontologically independent. Parts of organs and even the organs themselves are identifiable (and parts of large organs are even bigger than certain individual organisms) insofar as they are part of the whole organism. Aquinas famously said that a severed hand is only a hand in name.
Now this small tangent into metaphysics is important for doctors, nurses, etc. because we use terms like "tendency" and "function" quite often. Once we reject the Humean approach to causality, then we must accept the fact that every organ has a characteristic function, a function that is natural to it. This is the basis of natural law ethics. And this is incredibly important for discussions in reproductive/sexual ethics.
Chris
