Example: Sufficient Condition of A+ MUST MEAN Necessary Condition of Studying occurred

  1. Temporally speaking, either condition can occur first, or the two conditions can occur at the same time. In our example, the necessary condition (studying) would most logically occur first. Depending on the example, the sufficient condition could occur first.

I understand the point above about temporal conditions on a hypothetical level. I can think of examples where both the necessary and sufficient conditions occur at the same time. But I cannot think of an example where the sufficient condition could occur first. Does anyone have any examples where the sufficient condition occurs first?

An example would help me crystallize the concept. Thank you!

  • 1
    Is this a quote from somewhere? What was 1.? It is hard to understand what you are asking without context. – Conifold Jan 9 '20 at 20:07
  • Yes, it is. It's just an explanation about the different features of necessary and sufficient conditions. The first point is "The sufficient condition does not cause the necessary condition to occur" which makes sense. It's not causality. Thank you! – lolhaha Jan 10 '20 at 15:35
  • Necessity - > must , sufficient -> may; In 2+n=4, it must be n is 2. In k+n=4, it is sufficient that n is 2, thus it may be that n is 2, as n varies with the unknown k. Until we know k, 2 is a value that suffices as n, and we are not bound by necessity. – J D Mar 10 '20 at 16:29

Long comment : at first sight, I agree with you.

We say that B is a necessary condition for A to mean: "if A, then B".

And we say also that A is a sufficient condition for B to mean: "if A, then B".

Thus, the Example:

Sufficient Condition of A+ MUST MEAN Necessary Condition of Studying occured,

amounts to :

"if you received an A+, then you must have studied".

Having studied is the necessary condition, and having received A+ is the sufficient one.

But this is logic, where there is neither "temporal" issue nor causal link involved.

I've have found this example regarding causal processes:

If x is a sufficient cause of y, then the presence of x necessarily implies the subsequent occurrence of y. However, another cause z may alternatively cause y. Thus the presence of y does not imply the prior occurrence of x. [For example, if it is sunny outside, then it is daytime. It being sunny is a sufficient cause for one to conclude that it is daytime. But just because it is daytime does not necessarily mean it is sunny outside.]

But IMO is highly debatable that the logical process (deducing, form the presence of sun light, that it is daytime) has a temporal aspect: we have daylight and sun at the same time.

Cause is prior to effect, but the logical process is from effect to cause : if the switch is on, then the light is on, is in general wrong: we may have a circuit break.

But, if the light is on, then the switch must be turned on.

  • Thank you so much, Mauro! Honestly, I'm still a bit confused: You spoke of both causality and temporality and said that logic doesn't address either. In terms of temporality, you gave an example where the necessary and sufficient conditions occur at the same time i.e. sun and daylight at the same time. The example I mentioned is one where the necessary condition occurs before the sufficient condition i.e. studying being necessary to obtain an A OR light switch on for the light being on. I still can't think of an example where the sufficient condition would occur first though. – lolhaha Jan 10 '20 at 15:39

If you parents were born of human parents, then you are human.

Your parents' birth is previous to your existence, yet their having human parents is a sufficient condition to your being human. Is that the kind of case you wanted?


I take the terms, necessary and sufficient condition, in their standard senses:

X is a necessary condition of Y ⇒ If X does not occur, then Y cannot occur.

X is a sufficient condition of Y ⇒ If X occurs, then Y must occur.

If there are sufficient conditions for an event, then the event must occur and either there are no necessary but only sufficient conditions, hence the sufficient conditions cannot precede them ('come first'), or the sufficient conditions are also the necessary conditions or include them, in which case neither the sufficient nor the necessary conditions can be prior.

For these reasons and unless someone can come up with a counter-argument, I can't see how a sufficient condition could 'come first'.

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