Home > Uncategorized > The neuroscience fallacy and the startling truth

The neuroscience fallacy and the startling truth

I want to draw your attention to something I think is quite important to think about, in regards to causality and its relation to the scientific enterprise. More particularly, I am concerned about a particular application of the scientific enterprise to how the modern world conceives of human thought, of the brain and of consciousness. My belief is this: the scientific project, when it comes to the brain, does not understand causality–in fact it routinely commits a very basic logical fallacy.

Quite a claim, you might say. I mean, science is supposed to be the discipline that makes sense out of the world. If anyone should understand causality, it is the scientists! I feel as I write this that I am perhaps making an obvious blunder. Yet, for the life of me, I cannot see what that blunder is. I spend much of my time immersed in logic, dealing with the world of mathematical abstractions, and I think that I’ve gotten pretty good at logic, as a result. And then I look around me and I see science using this very same logic, to deduce causality, in a way that seems to me to be completely backwards.

Let me explain what I mean. Probably the most basic concept in logic is that of a syllogism: A implies B. A syllogism is an “if, then” statement. It looks nice to write a syllogism with a little arrow:

A \rightarrow B

This helps us visualize the direction of the logic. We use syllogisms all the time! Here are some examples.

1. If it was raining, then I would have used my umbrella.

2. If the Yankees win the world series this year, I will shave my head.

3. If you don’t eat your meat first, you can’t have any pudding.

Forget the fact that none of these statements are actually true in general. The point of these is examples are not their truth or falsehood, but their form. Now, for any syllogism, there is another simple syllogism that is logically equivalent to it. Logically equivalent means that the two statements imply each other–if you know one, you know the other. The syllogism that is logically equivalent to a given syllogism is called its contrapositive: NOT B implies NOT A. In symbols, it is usually written something like this:

\neg B \rightarrow \neg A

Thus the little symbol “\neg” stands for “not.” Here are, in words, the contrapositives of the above statements:

1. If I do not use my umbrella, then it was not raining.

2. If I do not shave my head after the world series this year, the yankees did not win the world series this year.

3. If you can have some pudding, then you ate your meat.

The equivalence of a statement and its contrapositive are self-evident logical truths.

A common logical fallacy, on the other hand, is to assume a syllogism is equivalent to its converse: B implies A. This is often called “affirming the consequent.” For example, just because I use my umbrella doesn’t mean it had to be raining. I could have used it, for example, to block the sun. Intuitively, we can see that statements are not equivalent to their converses because, as a rule, the same event can be brought about by different causes. For example, I might frequently use my umbrella to block out the sun as well, demonstrating that the converse of statement 1 is false.

Now, bear with me here, because things are about to get a little tricky. Often the fallacy of affirming the consequent occurs because one considers the contrapositive of the converse instead. The fallacy is believing that “A implies B” entails that “NOT A implies NOT B.” Since the logical implication “goes in the same direction,” it is easy to make this mistake.

Now, I believe that modern scientific thinking often ignores this basic logical fact in the way that it approaches its understanding of causality. Further, I think that it has ignored it because it has a materialistic bias, and thus the consequences for accepting it are startling and at odds with the philosophical presuppositions of modern scientific thinking.

It is especially clear to me that the project of neuroscience falls victim to this logical fallacy. Neuroscience, or at least the popular interpretation of it (and, I suspect, the internal beliefs of most neuroscientists in regards to what they think they are accomplishing) is practically built upon making this error.

Consider first an example. Scientists do a study, and find:

1. The removal of physical circumstances A results in the disappearance of mental state/experience/event B.

Then they conclude:

2. Therefore physical circumstances A cause mental state/experience/event B.

If we consider this as a syllogism, it is clearly the logical fallacy I described above.

For example, scientists may discover that feelings of depression and unhappiness are associated with lower levels of serotonin in the brain (I haven’t verified this, by the way–I might have the science part wrong here). By correcting this imbalance, the scientists are able to remove the feelings of depression. Now, I hope no one misunderstands me here. I believe that this sort of thing, if done responsibly, is very good. But I think that we misunderstand what is going on here, tragically, in a way that undermines our understanding of the human soul.

Many people, upon hearing that we now have a pill that cures depression by altering a chemical state of affairs in the brain, will conclude that this state of affairs causes the mental condition known as depression. They will say things like “my emotions are nothing more than a chemical state of affairs.” And the scientists their will support them in this conclusion. The logic, however, actually ought to go in the other direction: if removal of the serotonin imbalance also removes the depression, then the contrapositive of this causal relationship, the only statement that logically follows from this experimental result, is that depression is the cause of the serotonin imbalance.

This conclusion, however, is unacceptable to modern neuroscientists, because their entire project is to reduce mental states to physical states. The reason they do this is, well, because they are afraid that not doing so would be unscientific. If they would accept that there is something like “mind” that is metaphysically distinct from “brain” and interacts dynamically with it, then the whole project of science, as they understand it, is undermined.

In a way they are right. But they need to get over it! We would do well to stop thinking about science as a special sacred realm of knowledge, as a special epistemological project. We need to get back to thinking about all things carefully and logically. We have reified science far too much, and this hinders our understanding of many things. But that’s a topic for another post…

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  1. Terence
    August 1, 2012 at 1:24 am

    I believe that a conflation of implication and causality is required to follow your argument. Specifically, the causality relationship “A causes B” and its contrapositive relationship “not B causes not A” are not equivalent.
    Take your umbrella example. I would hardly expect you to believe that a responsible fellow who is impelled to bring an umbrella on every outing with any reasonable chance of rain, can remove such a possibility by simply leaving his umbrella at home.
    David Hume had no problem with his contemporaries’ handling of implication, but that of causality. His Critique of Pure Reason does well not only to raise his concerns but to distinguish these two concepts from one another. His example of the two clocks provides a great example with which to tease them apart.
    Anyhow, I think you are on to something with regards to a current chicken/egg dilemma regarding seratonin’s role in out brains, but I don’t believe that there is a direct violation of logic lurking here.
    It is true that the materialist reductionism that you criticize is not a logical consequence of the evidence at hand, however, making such leaps of reason is not equivalent to a blatant disregard for logic. If it were, then all of pragmatism would be at fault, not just the world of neuroscience.
    To play the devil’s advocate, the antidualist materialist could ask you to provide an observable difference between emotion and the chemical state of one’s brain, of course requiring a definition of emotion that would not preclude its identity with a chemical situation a priori.
    It does seems strange that neuroscience is filled with examples of treatments which consist of adjusting the electro-chemical status of a brain to more closely approximate a model of health, with no understanding of the mechanical relationship between such stati and psychological health. Most strange is the frequent efficacy of such treatments. A philosophically troublesome state of affairs to be sure.

  2. August 3, 2012 at 12:44 pm

    Terence, good thoughts there. You are right to bring up the distinction between causality and implication; the relationship between these two things is, I think, something that deserves a lot of thought. It is mysterious to me, and I believe that a lot of our present confusion about the nature of causality can be revealed by probing this relationship.

    In regards to the umbrella example, I think that this is great to think about. I would argue that causality is not actually apparent in either direction (that is, in regards to both the statement and its contrapositive). We find it plausible and acceptable to say that the rain made the man bring his umbrella: that the rain caused him to do so. But we find it unacceptable to assert the contrapositive: that his not bringing his umbrella caused it to not rain. My question is: why? I’m not being silly here; I think something very deep is at play in this asymmetry.

    We think that a man who believed that he could stop the rain by not bringing his umbrella would be a foolish man. That strikes us as implausible. But why? One natural response would be: because it could still rain. However, that’s not exactly fair. We could just as well say, to negate the man’s claim that the rain causes him to bring his umbrella, that “the man could forget to bring his umbrella when it rains, or his umbrella could be vaporized by an energy beam as he is exiting his house, etc.” The point is, we are supposed to be considering a universe in which the logical implication definitely holds: whenever this man brings his umbrella, it rains. In such a universe, we think that he has the right to believe that the rain causes him to bring his umbrella. But in such a universe, does he also have a right to believe the contrapositive: that him not bringing his umbrella causes it to not rain? We say that he is not allowed to think this. I find this interesting.

    What about the man who believes that the rain caused him to bring his umbrella? Is he not equally foolish in not considering alternative possibilities like those mentioned above? If not, why not? Again, I think this is a very deep issue. It has to do with how we–modern Western people, and not necessarily everyone throughout history–conceive of our agency in the world. We are naturally repelled by certain sorts of ideas of how our internal decisions, states of mind, or whatever, affect the outside world. We regard them as superstitious. But other sorts of ideas of how our internal decisions and states of mind affect the outside world are perfectly acceptable to us.

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