Condition
Just one more term, and I'll give an example that will try to tie all this together.
A condition is the cause of a cause.
That is, if the cause of a given effect can't do its job of removing the contradictoriness unless some other fact is true, then this other fact (which explains how the cause can be a cause in this case) is a condition for the effect.
The condition, as so defined, isn't really a cause of the effect; because, given the cause, then all that is necessary for the effect to make sense is there--and the cause is all (and only) what is necessary for the effect to make sense. And of course, the cause as a fact makes sense somehow, either by itself or by some other fact which makes sense out of it. And all you need to explain the effect is the fact which is the cause; you don't need the explanations of how the cause got to be this fact; it is enough (for the effect) that it's there.
Nevertheless, if the cause is not self-sufficient ("self-explanatory"), you may wonder how it can be there, since there's something about it that says it couldn't be there. In that case, you're treating (what is in fact) the cause as itself an effect of some cause. And of course this "cause-of-the-cause" also in fact has to "be there" for the original effect to make sense, because if it isn't there, then the cause isn't there, and if the cause isn't there, the effect (as a real contradiction) isn't there either.
So having once seen the cause as the effect of its own cause, you can now see an indirect dependence of the effect on this "cause-of-its-cause"; but this is not the same kind of dependence as that of the effect on its cause, because you can't intellectually "stop" with the effect and ignore its cause (because then you are accepting a contradiction as real), whereas you can stop with the cause if you want to, because it, as a fact, is all that is needed to make sense out of the effect, and your mind then can accept the situation as making sense.
Hence, this "cause-of-the-cause" is not really a cause of the effect (something without which it is unintelligible), even though indirectly the effect couldn't be what it is without it (because the cause couldn't exist without it). Hence, this fact which is indirectly "necessary" to the effect has the special term "condition" attached to it. In relation to the cause, the condition for the effect is, of course, a cause; in relation to the original effect, it is not a cause but a condition.
Traditionally, conditions were thought of as "removing what prevents" the cause from "operating"; but that means that without the condition, the cause would not be able to "operate," and so the effect could not occur; and that means that the cause as cause would be impossible without the condition. Or, in other words, the condition is what is necessary for the cause to be what it is, or that without which the cause as cause would be a contradiction--which is another way of saying that the cause is an effect of the condition.
For instance, the color slide in the projector was said to be the "condition" for the picture on the screen, because the "cause" was the light hitting the screen, and the slide got in the way of the light, blocking out certain colors and so on; it allowed the light to do its job of putting the picture there; but the light was what "did" the job.
Translating this into my terminology is not perfectly straightforward, because what the cause is and what the conditions are depend on how you define the effect (i.e. what aspects of the concrete situation there in the darkened room you choose to pick out as unintelligible-by-themselves). If you are interested in the particular pattern of colors of light on the screen (when a moment ago there was a different one, say, and you've got the same apparatus), then the cause is the pattern on the slide in position in front of the light. If, however, you are interested in how the screen isn't black like the rest of the room, then obviously the cause is the light of the projector as it reaches the screen. But since in fact not all the light from the bulb gets to the screen because of the slide in the way, then the slide is now the condition for the light's actually striking the screen (as can be seen from the fact that if there were a totally black slide in there, the screen would be black).
Anyhow, that is the relation between "condition" in my sense of the term and the traditional sense of "condition" as "removens prohibens" ("removing what is preventing"). The point that is interesting for the purposes of philosophical (and for that matter, scientific) method is that you don't need to go back to conditions to explain an effect. The effect is explained once its cause is known to be a fact; any explanations of how this fact can be a fact may be interesting and worth exploring, but are not needed in order to explain the effect.
Of course, there are proximate and remote conditions for a given effect. The "proximate" condition would be the cause of the effect's cause; a remote condition for this effect would be a condition for the effect's cause. That is, there is no law that says the condition (the cause-of-the-cause) can't itself be the effect of some more remote cause, nor that that can't also be the effect of a still more remote cause of it, and so on and so on.
And it is true that if any of these more remote conditions were not there, then the condition on the next lower level would not be there (because, lacking its cause, it would be a contradiction, and so wouldn't exist)--which would mean that none of the conditions below it would exist, which would mean that the cause wouldn't exist, which would mean that the effect wouldn't exist. So the non-presence of any of the conditions means that the effect is a contradiction (since it indirectly depends on each of them). This is what Kant was saying in the introduction to the antinomies of pure reason when he said that all the conditions for any "event" (effect) have to be given if the effect is given.
But the point here is that you don't have to go back to "the first cause" or "the ultimate condition" in order to explain any given effect. Depending on how curious you are, you can stop at the cause, or you can go back to the first-level condition, or you can go back a step or two further and stop at the fourth-level condition, or whatever. Wherever you stop, you stop at what is a fact, however it got to be that way, and so what is below it (i.e. explained by it) makes sense.
Let me stress this point as another conclusion:
Conclusion 6: An effect is explained by its cause; it is not necessary to have recourse to conditions to explain the effect. On the assumption that the cause is a fact, the effect makes sense.
Is there, by the way, a "first cause" or an "ultimate condition," or can there be an infinite sequence of causes needing causes? The answer is not perfectly straightforward, and it turns out that in some cases (those where the cause doesn't have to be in existence while the effect exists, but merely has to have existed at some time) there could be an infinite sequence, but in others there couldn't; but we will leave this for later, when we actually start applying all this apparatus we have developed about effects and causes.
Let me now give an example to tie all these terms together. Let us say that you notice that the earth is warmer on the day side than it is on the night side. Since the earth is a single whole, by itself this difference in temperature does not make sense. Therefore, the cause of this effect is whatever it is that accounts for the bright side of the earth's being hotter than the dark side.
Now we know that the sun is emitting radiation of many wave lengths, heat as well as light, and it is not at all surprising to find that the side that the light is hitting is also the side that the heat of the sun is hitting; and so our cause is the fact that the light of the sun at the earth's surface also contains heat. Add this fact to the effect and it makes sense to say that the bright side is hotter than the dark side.
Now then, the earth (with its dark and light sides) is what is affected. The effect, as I said, is the fact that the bright side is warmer than the dark one. The being affected of the earth is the warming of it by the heat that accompanies the light of the sun (i.e., perhaps more accurately, its being warmed by the sun's heat). The causality of the cause is the heating of the earth by this heat that accompanies the light. And, of course, the cause is just the heat itself, which is just heat and is not altered by the fact that the earth is being warmed by it (as can be seen from the fact that this much heat is also at any point this same distance from the sun, but there's no planet there getting warmed by it).
The causer in this case is the "thing" you would point to in answer to the question, "What is doing this?" And in this case, we would in all probability say "The sun." That is, in ordinary language, the sun is the "cause" of the warming of the earth. If you happen to have a more scientific bent, and think of the photons of heat and light as "somethings" in their own right which "escaped" from the sun, then they (the electromagnetic radiation itself) would be the causer, because these photons in fact have properties beyond what is merely necessary to account for the warming of the earth (they exert pressure on it, and there are X-rays and so on which are neither light nor heat).
If you consider the photons as the causer, then the sun would be the condition for the warming of the earth; because without the sun, the light-and-heat wouldn't be there, and the effect wouldn't occur. The sun is actually a condition for the effect even if you consider it the causer, because the causer, as concrete, can include all sorts of aspects within it; and in fact it would include the cause of the light's being at the point where it can act on the earth. Whatever it was that got the sun into a state where it emits light would, of course, be a more remote condition for the warming of the earth; and so on.
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