The pro-abortionists sometimes use the analogy of an acorn not being a tree in order to demonstrate that a fetus is not human. They say that just as the acorn has the potentiality to be a tree, the fetus also has the potentiality to be a human; but since potentiality is different from actuality, it follows that the fetus is not actually a human, and the acorn is not actually a tree.
Also, let's assume for the moment that the tree in question is an oak tree, and the acorn is from that oak tree. The problem with the above argument is that the acorn is by nature oak. It is not a tree. By definition, a tree is a fully developed plant. An acorn, by definition, is an undeveloped plant. Therefore, to say that an acorn is not a tree is correct, but it is still oak by nature. Their analogy is not a correct analogy anymore than saying a baby is not an adult, and therefore the baby is not human. By definition, a baby is human and so is an adult. Therefore, the problem with this defense to support the aborting of babies is that it uses an improper pairing of words without dealing with the nature of what those words represent.
Let's look at it again. The oak acorn is by nature oak since it has oak DNA. Likewise, a fully developed oak tree is also by nature oak since it has oak DNA. The difference is that one is fully developed, and the other is not. The same goes with the life in the womb of the mother as compared to a full-grown adult. A baby is not an adult, but both have the nature of a human. Therefore, the attempted justification of the pro-abortionist is illogical and invalid.