Quick Response #28: An Acorn Is Not an Oak Tree, So a Fetus Is Not a Child

Judith Jarvis Thomson is famous for the Violinist argument from her paper “In Defense of Abortion,” but she actually begins it with another well-known analogy: since an acorn isn’t an oak tree, a fetus shouldn’t be considered a child. Emily Albrecht explains why Thomson’s acorn analogy, while popular, is a fallacious argument that isn’t a problem for the pro-life position.

Related Links:

Quick Response #1: The Embryo Isn’t Human – https://youtu.be/DrPyygzz43E

Quick Response #2: The Embryo Isn’t a Person – https://youtu.be/c6_kwErY4OE

Quick Response #5: Women Have the Right to Refuse the Use of Their Bodies – https://youtu.be/Lv7HXpAY_yU

Pro-Life Apologetics: The Equal Rights Argument – https://youtu.be/louYc-9cvE0


A fetus is not a child for the same reason an acorn is not an oak tree! It’s a classic analogy thanks to Judith Jarvis Thomson’s famous paper “A Defense of Abortion.” While Thomson’s Violinist thought-experiment is the most famous part of her paper, and you can find our response to that in Quick Response #5, her “an acorn isn’t an oak tree” statement has been gaining popularity because it seems so ridiculously clear-cut. OBVIOUSLY an acorn isn’t an oak tree, so pro-lifers are delusional to claim that a fetus is in any way comparable to a child. But this acorn to oak tree analogy mixes up scientific terms in the hopes that you get lost on the way and come out pro-choice. 


Yes, an acorn is not an oak TREE, but an acorn IS an oak. Tree is a stage of development for that species—the oak species—like an adult is a stage of development for the human species. In other words, an oak tree is like an adult of the species oak. If an oak tree is analogous to a human adult, and an oak acorn is analogous to a human fetus, then saying an oak acorn is not an oak tree is like saying a human fetus is not a human adult; DUH! 

But an acorn is an OAK just like a fetus is a human – we’re talking about the species here. “Oak tree” is specifying two things in those two words: oak is the species, tree is the stage of development. We usually don’t say “oak acorn;” we just say “acorn” even though it would be more technically correct to say “oak acorn,” and THAT little lack of clarity with our language is doing A LOT of the heavy lifting in this ridiculous analogy. An acorn is an oak, and a fetus is a human.

Once fertilization is complete, a living member of the species Homo sapiens exists. Of course it’s not an adult, but it is a human, and I think that all living humans deserve an equal right to be protected from violence. We discuss the biology of the unborn and why they are persons deserving equal protection from violence in Quick Response #1 and #2, respectively.

There’s another variation on the “acorn isn’t an oak tree” argument that is, at least on its face, a bit more convincing: flour, eggs, butter, sugar, salt, milk, and baking soda sitting on my counter in a mixing bowl is obviously not a cake. If I treated it like cake and just ate a giant bowl-full, I could get really sick! Cake batter is fundamentally different from cake because, even though the ingredients are the exact same, spending time in the proper environment for the proper amount of time—AKA the oven—is necessary to make it into cake. Similarly, a pro-choice person might say “sure, a fetus has all the same ‘ingredients’ as an adult human—it’s got human DNA and such—but those 9 months of development are crucial to it becoming an ACTUAL human.” 

While the “acorn isn’t an oak tree” argument relies on misunderstanding species versus stage of development terminology, the cake batter one thinks more about how “cooking time” so to speak changes the same set of ingredients into something totally different that we should treat distinctly. But here’s one important difference between cake ingredients sitting in a bowl and a day-1 zygote: the human zygote will grow itself into a larger and more complex human being, but the cake ingredients can’t mix themselves, much less put themselves into the oven and bake into a cake! Even the tiniest human is a consistent, organized, self-directed organism from its earliest moments, not a jumble of “ingredients” that might one day become a human adult.

The two different versions of the acorn analogy mislead peoples’ moral imagination in different ways, but both are designed to prevent people from seeing the truth that a human being is in an identity relationship with itself throughout its life; that is to say, none of the changes that happen to a human from fertilization to death fundamentally change who or what that person is.

I’ve never argued and am not going to argue that a fetus is literally the exact same thing as a human toddler. There’s tons of differences between the two—a lot happens during pregnancy, and in the first 18 years of a person’s life, for that matter! The question is whether any of those differences are morally relevant. While both a fetus and a toddler are biologically human, there’s much debate about whether other traits that develop later on like sentience, the ability to feel pain, or self-awareness are what makes a biological human a person who should have rights. We discuss this idea extensively in our video on The Equal Rights Argument, link in the description. The moral of the story? The traits that make a fetus different from an infant or a toddler aren’t morally relevant. The only logical way to affirm equal rights for all born humans is to protect the unborn too.

Please note: The goal of the comments section on this blog is simply and unambiguously to promote productive dialogue. We reserve the right to delete comments that are snarky, disrespectful, flagrantly uncharitable, offensive, or off-topic. If in doubt, read our Comments Policy.