By Inside_my_head.jpg: Andrew Mason from London, UK derivative work: -- Jtneill - Talk (Inside_my_head.jpg) [CC BY 2.0 (], via Wikimedia Commons
Reading Time: 7 minutes By Inside_my_head.jpg: Andrew Mason from London, UK derivative work: -- Jtneill - Talk (Inside_my_head.jpg) [CC BY 2.0 (], via Wikimedia Commons
Reading Time: 7 minutes

We often see rationality popping up as a property that humans apparently exclusively have. This appears in several arguments, most notably those concerning personhood (and thus abortion) as well as famous arguments like CS Lewis’ Argument From Reason. I am going to look at what rationality is and hopefully show that it is not uniquely human or what people oft4en assume it is.

Recently, Vincent Torley set out his argument against abortion:

1. Any organism whose development into a rational human adult is internally regulated is a human individual. (Definition)

2. By this criterion, a one-cell embryo is a human individual.

3. Rational human adults possess an intrinsic moral value: that is, their value is not conferred on them by society, or even by God. (Assumption.)

4. No abilities or qualities (e.g. sentience, rationality, self-awareness, knowledge of other minds) which are subsequently manifested in a human individual can add to its value as an individual, because their manifestation is the result of an internally regulated process, where any new information imparted to the developing embryo/fetus/infant from the outside world has to be absorbed by the individual in accordance with its internally regulated plan of development. (Just to be clear: I’m assuming this plan is purely chemical.) Putting it another way: value derives not from the information added to a developing individual, but from the meta-information embedded within it, without which it could not make use of this information. That’s primary.

So, for Torley, at least, rationality is a key component for human exceptionalism and for ascribing to us (moral) value over and above other species.

As far as the Argument From Reason is concerned, it can be summed up as this commenter has done:

Jonathan talks of “our rational nature”.
– But how does a non-rational process (i.e. evolution) produce a rational nature?
– How would the very first supposedly rational creature know it was rational?

A very good book that offers a great rebuttal to Lewis, and later Victor Reppert, in their application of this argument, is John Beversluis’ C S Lewis and the Search for Rational Religion. (It is also worth reading “Anscombe’s Critique of C. S. Lewis’s Revised Argument from Reason” by Gregory Bassham.)

As Wikipedia expounds:

One absolutely central inconsistency ruins [the naturalistic worldview]…. The whole picture professes to depend on inferences from observed facts. Unless inference is valid, the whole picture disappears…. [U]nless Reason is an absolute–all is in ruins. Yet those who ask me to believe this world picture also ask me to believe that Reason is simply the unforeseen and unintended by-product of mindless matter at one stage of its endless and aimless becoming. Here is flat contradiction. They ask me at the same moment to accept a conclusion and to discredit the only testimony on which that conclusion can be based.

— C. S. Lewis, “Is Theology Poetry?”, The Weight of Glory and Other Addresses

More precisely, Lewis’s argument from reason can be stated as follows:

1. No belief is rationally inferred if it can be fully explained in terms of nonrational causes…

2. If naturalism is true, then all beliefs can be fully explained in terms of nonrational causes.

3. Therefore, if naturalism is true, then no belief is rationally inferred (from 1 and 2).

4. We have good reason to accept naturalism only if it can be rationally inferred from good evidence.

5. Therefore, there is not, and cannot be, good reason to accept naturalism.[1]

Which is essentially to say that (deterministic) evolutionary mechanisms are not rational, so how could they bring about rationality? Alvin Plantinga later used this to formulate the EAAN – Evolutionary Argument Against Naturalism – that evolution, as a nonrational process, is not interested in finding truth in the world (to vastly simplify it).

Back in the 1940s, when Elizabeth Anscombe criticised CS Lewis’ argument, she pointed out issues with defining rationality. (See “The Argument from Reason: Lewis’s Fundamental Mistakes” by Davi Kyle Johnson.)

So, “How can humans be rational because rationality can’t emerge from the non-rational”. Of course, the first thing to say here is, “Why not?” Any theory of emergence will argue that properties that are categorically different can emerge from other entities with different properties. Life emerges (albeit on a naturalistic thesis) from non-life. Patterns emerge from murmurations of starlings, consciousness from brain matter and so on.

Of course, this is just an inverse form of the Fallacy of Composition known as the Fallacy of Division. A fallacy of division occurs when one reasons logically that something true for the whole must also be true of all or some of its parts. How can a computer compute when a single piece of plastic that makes it up, or the screen, or any individual part, can’t? These properties emerge when certain networks and pieces of matter are arranged in a particular way.

I have argued before that evolution will favour the rational because of the pragmatic implications. That is to say, if I reason that the swaying bush is a tiger, rather than that it has no causal basis, then I am more likely to survive. I reason with myself, using induction here, that the bush is a tiger, then whether it is or not, I will survive. Imagine a Caroll Diagram whereby there are four options:

  1. I hypothesise tiger, run away, it is tiger, SURVIVE
  2. I hypothesise tiger, run away, it isn’t tiger, SURVIVE
  3. I hypothesise nothing (using no rationality), stay put, it is tiger, DIE
  4. I hypothesise nothing (using no rationality), stay put, it isn’t tiger, SURVIVE

In other words, death comes to the person who does not use rationality. Therefore, using rationality will be selected in by evolution by natural selection.

You can apply this to all sorts of things, such as hypothesising about food, problem-solving and so on. Truth has a pragmatic value to us in terms of survival and, arguably, successfully doing almost anything.

The main point on this, however, is that it prompts the question about what rationality really is. A computer is rational and adheres strictly (much better than humans) to logic and rationality, if the word is described in logical terms. But a computer isn’t alive. It is made of inanimate pieces of natural matter. Rationality is thus not the exclusive domain of humans. Indeed, other animals show rationality to differing degrees. Dogs, primates and so on…

I think this is a key point because adherents to the Argument from Reason often fail to properly define rationality, and often seem to conflate it with deliberation – thinking about rational ideas. But deliberating on a decision is actually just very inefficient (qua poor) rationality. If we were to be purely rational in our computations, then our conclusions would be instantaneous. This is why God, if she was to exist, wouldn’t think, wouldn’t deliberate. Perfect decisions and decision-making would be non-deliberative.

This is a really important point to make; rationality isn’t just thinking or deliberating. These are just very crappy applications of or attempts to arrive at rationality. In this way, computers utilising logic are much more efficient rationalisers than humans.

Rationality, for me anyway, is the application of logic and logical rules and this has pragmatic implications, as seen above. And good logic is logic from which usefulness can be derived. Otherwise, logic would be rubbish. If, for the sake of argument, logic and rationality produced uselessness or deleterious consequences, then no entity would favour it since they would end up not existing due to its negative consequences. Rationality is useful, and that is why we have evolved to use it.

The second part of point of the commenter’s above point is just a little bit odd. “How would the very first supposedly rational creature know it was rational?” Well, if we observe something, and then give that thing a label, then that’s how. Technically, we would need to evolve complex language and communication, as well as decent sensory organs. With that, we can start to understand the world. Logic is a language of description about the world that we use because we can and it’s useful. I posit that this person thinks he’s being clever by offering one of these eyebrow-raising “thoughtful” questions, without realising that the question is a bit empty.

“How would the very first supposedly seeing creature know it was seeing?” You could replace the words there with any kind of idea, but what the question really is, is the Cartesian “How do we know anything?” Descartes answered this by saying we only know one thing to be indubitably true – that the thinking entity exists – cogito ergo sum. Other than that, it is all ranges of probability.

We know we are rational because we define rationality (R) as X, observe ourselves having X and say (using logic), “R is X; we have X; therefore, we have R.” His question is, arguably, “How do we know we have X?” and this will come down to axioms and probabilities. We don’t know (indubitably) we are not in The Matrix, but we can use some useful arguments to try to answer that.

Perhaps, for any form of suitably complex life, (potential) grasp of logic is a priori? Other animals appear to have a grasp of simple rationality, including dogs. Pavlov’s Dogs looks at a form of intuitive inductive reasoning, whereby inductive reasoning is inbuilt into the dogs’ physiology. If the commenter wants to make sweeping statements, perhaps he should read up on certain ideas first: he could do with starting off with, say, the Wikipedia entry on “Animal Cognition“. Certain species are adept at problem-solving, which requires reasoning.

Do any of them know they are rational? No, because they don’t understand the word or those concepts. Why? Because they lack the language. Language and ideas are coextensive. Early humans would not have understood love or pride in any definitional sense (they might know they are feeling a thing that we might call pride). These ideas, or at least the understanding of these ideas, are built up upon language. the more complex the idea to understand, the greater the range, understanding and application of language needed to understand or know these things.

And yes, we need to define know.

To return to notions of personhood and abortion, by “devaluing” or “reducing” these ideas of rationality, we pull the rug out from people who assert human exceptionalism and value arguments for personhood. Personally, what I think separates (or throws us further along a continuum) from other species is our ability to have language and complex communication, and opposable thumbs (i.e. tools).

More explicitly, let’s analyse this opening premise:

1. Any organism whose development into a rational human adult is internally regulated is a human individual. (Definition)

What Torley is doing is using rationality as the driving property here, because you could substitute the word “human” for any other word (species etc.) and you would get a similar conclusion. The power, for him, of internal regulation is precisely because it leads to rationality, but without really looking at what this term means, Torley is leaving his argument rather underdeveloped. It may or may not have some future potential or value, but as I see it now, his argument has no value, and so I can feel it acceptable to reject it.


Stay in touch! Like A Tippling Philosopher on Facebook:

Please also donate to my MS treatment appeal (I have just been diagnosed with Primary Progressive Multiple Sclerosis) so I can keep doing what I do!

A TIPPLING PHILOSOPHER Jonathan MS Pearce is a philosopher, author, columnist, and public speaker with an interest in writing about almost anything, from skepticism to science, politics, and morality,...

Notify of
Inline Feedbacks
View all comments