“That’s not logical captain…”

Spock loves to say “logical,” and the other members of the Enterprise crew hold that Spock is “logical” and that McCoy is “emotional.”

News flash, everything you learned about logic from Spock is wrong. When Spock says “logical,” he means that something is a good idea, or the smart thing, or the likely answer to a problem. In this misuse of the word “logical,” science is logical, statistics are logical, and emotions are decidedly “illogical.”

Real logic breaks down into two kinds: deductive logic and inductive logic. Deductive logic consists of arguments which have a link of necessity between their supporting statements and their conclusions. In other words, if you accept the supporting statements, you can’t argue with the truth of the conclusions. Examples of this kind of logic are 2+2=4, “either the keys are here or they are somewhere else, they aren’t here, so they must be somewhere else,” and so on. These arguments are described as “valid” because the supporting statements (premises) guarantee the truth of the conclusion (provided that they are true themselves).

On the other side is inductive logic. Inductive logic, by definition, is never ever valid. The truth of the conclusion is not inescapable even if the premises are all true. It may be the case that 99% of all cases end in a particular way, but that does not guarantee that this particular case will end that way. All inductive logic is invalid by the deductive standard. Just because something has never happened does not guarantee that it never will (so much for statistics), and just because something has always happened up to this point does not guarantee that it always will (so much for science).

Inductive logic does not deal with any degree of certainty, only of probability, and even that probability is never more than an approximation. When one leaves the surety of deductive, valid, logic and enters inductive territory, all pretense of certainty ought to be abandoned. Inductive logic is “soft logic” because of this squishy property of never offering any degree of certainty. Deductive, mathematical, logic is “hard logic” because the structure of the argument makes the conclusions rationally necessary.

So back to Spock. Spock speaks almost exclusively from the perspective of soft logic, squishy logic. He is well endowed intellectually and boasts a broad understanding of science and statistics and rational decision-making models. He speaks for moderation and proven methods. This is all well and good. However, he speaks of these soft logic enterprises as though they had the same rational weight as hard logic. It is this soft-logic-in-hard-logic’s-clothing that so irks me about his use of the words “logical” and “illogical” to describe things which are no more rationally established than what one happened to have for breakfast.

Mistaking soft logic for its more reliable counterpart is dangerous and criminally dishonest. Scientists who don’t fathom the differences (the scientific method relies on soft logic making it categorically invalid in all positive results) make bold claims about what is possible without the slightest shred of hard logical evidence to support their claims, regardless of how strong these claims may seem inductively. The scientist who speaks of “confirming” theories by observation does not understand the logical framework upon which his or her entire enterprise rests. Scientists who voice atheism as being rational do not understand rationality, or even what science is in the first place. This point is not a matter of mere opinion, but one which is rationally established through the certainty of deductive logic. The Eighteenth century philosopher David Hume established the logical problems inherent in the scientific method irrefutably over two hundred years ago. This is not new news.

Is science incredibly useful? Absolutely! Is it very good at understanding the natural world and the principles by which it operates? It seems to be. However, this success is inherently inductive, which means that we cannot rationally claim certainty for any of our claims beyond their effects. We can know the effect, but not directly the cause.

I may have to write more thoroughly on this topic later to clarify my point and make concrete the differences between inductive and deductive logic. For now let it suffice that inductive logic lacks the logical property of necessity, which means that its conclusions are never guaranteed. This means that there is always an element of uncertainty inherent to any inductive conclusion, regardless of how much evidence is involved. I hold that to deny this uncertainty is dishonest and immoral. Scientists should not pretend to be mathematicians. Spock should not pretend to be “logical.”