At a train station nearby, workers have extended fencing around a battery of new electrical equipment and attached a sign reading Trespassing Not Allowed. The old fencing that guards the adjacent area has its own sign, but that one reads No Trespassing. Why the change? Who could possibly know. But whatever the reason, the two statements give us a great opportunity to review the first fundamentals of critical thinking.
That term critical thinking covers a lot of ground, but we should be aware of two large distinctions to be made when we speak of thinking rationally: logic and dialectic. We often use the term logic as a synonym for critical thinking, but in stricter terms it refers, as Aristotle explained, to the principles special to a particular science. The science of navigation, for example, includes the principles of mapping, the directions of the compass, angles, measurement, and geometric relations. The science of grammar, on the other hand, includes the principles of words, phrases, clauses, etymology, and syntax. Phrases and clauses have little to do with navigation, and the points of the compass have nothing to do with the science of language. Each is special to a particular science, which is defined as an organized body of facts.
Dialectic, however, is something different. It is still a rational endeavor, but its concern is the general principles which all sciences depend upon. Whether the subject is navigating or writing, we are talking about something, and whatever that something is, we can understand it in relation to something else, either similar or different. We know that one thing can be the cause of something else, and that another thing will be the effect of that cause. These general ideas common to all subjects are gathered under a notion called in classical philosophy the topics, and they provide the basic questions we can ask of a subject in order to develop it rationally. For these reasons, the classical understanding of dialectic has been defined as “conversational thinking,” because it raises the general questions that arise in intelligent discussion. (An excellent article entitled “Looking for an Argument” by Manuel Bilsky et al. explains how to use the topics in finding something to say about a subject. You can read that article online by searching for it at jstor.org. It also appears in Edward P. J. Corbett’s Classical Rhetoric for the Modern Student, 1990.)
But both logic and dialectic begin with the idea that the world is made up of things, the rhetorical way of putting which is to ask, what are we talking about? And since one way to lose control of a rational understanding about the world is to change the definition (sometimes knowingly, sometimes not) of the same word or phrase through the conversation, the science of logic requires that any natural statement in words must be converted into what is called a proposition, a statement which connects a subject with a predicate through the verb to be, the primary copula in English. Thus, when that new sign on the fence says trespassing not allowed, logic will transform that for analytic purposes into trespassing is not something allowed. (Logic cares little for style, only rational clarity.) And for our purposes here, what we should note is that the negative appears in the predicate: is not something allowed.
Now the old sign on the fence said no trespassing, which in the propositional form of logic might be stated as no trespassing is an allowable thing. Here, the negative appears attached to the subject, and if we had to find some meaningful difference between the two statements, perhaps it’s this. To trespass (according to the estimable Black’s Law Dictionary) is “to gain or intrude unlawfully upon another’s land, property, or authority,” which makes it clear that, in the present context in which the sign appears, there is no such thing as lawful trespass. And so when the first sign negates the predicate, and not the subject, it leaves in the air the unspoken suggestion, the implication, that somewhere or sometime else, trespass might be allowable. The older sign, though, in negating the very thing which is the subject of the statement, no trespassing, is telling the reader that no such unlawful action is allowed there. The adjective no, together with the absence of the predicate adjective allowed, precludes any wavering about it: trespassing, which you know is illegal, is never allowed anywhere, so don’t do it here.
The critical thinking we call logic is meant to transform temporarily our natural thoughts into a special form which its science can then examine efficiently. If we learn how to do that, even if no further than the elementary stages of converting our natural sentences into logical propositions, then we will be able to give ourselves a way to see into the bony structure, so to speak, of our thinking. That skeleton, analogous to the anatomical one, must be strong to successfully support the conclusions we wish to draw. If our own thinking, and the thinking of others who wish to convince us that what they are telling us is true, can pass that rational stress test, then we can gain a measure of confidence in both ourselves and others. Both those signs at the train station are imperatives in purpose and force, and so properly they lie beyond logical treatment. But behind every command is a presumption, and if we can find and logically understand that, with the help of logic, we can gain a more comprehensive insight into what we are being asked to understand. And that is never time wasted.
***