In general, meaningful propositions look like:
There are some recognizable x1, x2,...xn such that x1~x2~...~xnwhere "~" means correlation. For example, "Tim is tall" means that I will correlate the experiences I would recognize as Tim with experiences I would recognize as tallness. Indeed, the correlation in the proposition is itself recognizable because correlations are inherently recognizable. We recognize both the subjects (xi) and the correlation specified by the claim.
I noted in my last post that we've made a mistake whenever we claim that one of the subjects is unrecognizable, since that contradicts our claim that we started by talking about meaningful things.
An unintelligible proposition is one in which we cannot recognize the subjects. For example, we may be told that "Kes qera tovu axia" is a proposition, but not know what it means because we fail to recognize the words as symbols for recognizable things or relationships.
However, a meaningless or nonsensical proposition is one that contradicts itself by claiming that it represents something recognizable and simultaneously claiming that its correlations are unrecognizable. For example, "all apparently uncaused events have undetectable causes," uses the dangerous word "undetectable." Undetectable is safe when used in a context, as in "undetectable with a Geiger counter," or "undetectable with the unaided eye." However, in-principle undetectability is a meaning-killer. We recognize the individual words in their respective contexts. We can recognize an event as a point in time and space where we see a transition of some kind, e.g., a transition in the trajectories of interacting particles. We recognize a cause as a correlation between the initial and final states of an event. We recognize detectability as a correlation of some kind. Yet, we would never recognize apparently uncaused events having inherently undetectable causes. Indeed, this is a prototypical nonsensical proposition - all of its subjects are recognizable, but its meaning is unrecognizable. Recognition and prediction go hand in hand, and that is why non-predictiveness is sign of meaninglessness.
I'll present one more test proposition: "pixies are undetectable with the naked eye." This proposition assumes that the pixies can be seen or recognized using techniques other than the naked eye. Otherwise, we would not know what it is we were talking about. For the proposition to make sense, we must know how to recognize a pixie in some fashion and with some degree of precision. For example, it is enough to say that a pixie is a tiny humanoid with wings. If we saw such a thing, say, through an ultraviolet camera, we would say, "Aha! A pixie!"