The walk sign is on iff the walk sign is on

I’m still not content with the walk sign issue. (Previously 1, 2.) Deciding what the walk signal means is apparently not as easy a task as I initially thought it was. In my last post I concluded that “the walk signal is there to tell pedestrians when they’re not going to be in contravention of the law by crossing the street.” On reflection, this seems horribly tautological – if there was no signal, people could cross whenever they wanted, assuming they were crossing at an intersection. Once there is a signal, then, according to my last conclusion, the only purpose of that signal is to inform people of when they’re in contravention of the law that supervenes on the very existence of the signal. The signal says when people are in contravention of the law; people are in contravention of the law when they disobey the signal.

P = “a pedestrian,” Y = “is obeying the law,” Z = “is obeying the signal”

(∃x)Px ,

(∀x)[(Yx⇒Zx)∧(Zx⇒Yx)] ,

Yx⇔Zx ;

Zx⇒Yx ,

Yx⇔Zx ,

Zx⇔Zx .

Choosing to cross on the walk sign, rather than on the wait sign, constitutes obeying the law. Thus, when the walk sign is on, the only thing the walk sign is signifying is that, if you were to cross, you would be obeying the signal. I could speculate that there are a bunch of cocky logicians working for city hall, but even if that was the case I would argue that having a signal installed only for the purpose of defining when people are and are not disobeying the signal is dumb, and there must be another reason why the signal is there. This follows from the whole concept of law ultimately being for the public good. I’m going to reiterate my earlier point that there must be some level of safety that’s implied by the walk sign being on, otherwise the walk sign wouldn’t exist. The walk sign must indicate, to some degree, that it is safe to walk, if only by a negation of the indication that it’s unsafe to walk when the walk sign is off.

(Feel free to correct me if my logic is off, it’s been a little while.)


One response to “The walk sign is on iff the walk sign is on

  1. I think that the walk signal is meant to indicate several things. When it is red, it indicates that it is illegal, and possibly unsafe, to cross. When it is green (or white, depending on your location), it lets the pedestrian know that they now have the right of way, and may cross, which is stronger than just that it is legal to cross. It does not guarantee safety, and certainly it would be prudent to exhibit caution when crossing, but the pedestrian does have right of way when the signal indicates walk. The safety of crossing is dependent on factors that the signal cannot predict–namely, how much traffic is present. The signal only knows which lanes of traffic have the right of way, not whether there’s actually traffic using those lanes.

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