(1) I said in my last post, “A Non-evident and Key Premise of Aquinas’s ‘First Way’”, that in this one I would set forth the second of Aquinas’s “Five Ways” of demonstrating that God exists in an explicitly syllogistic format. The aims are three: that of making its parallelism with the “First Way” evident; that of making it evident that the argument is perfectly valid; and that of showing that it is not evident that the argument is sound by isolating a key premise the truth of which is not evident.
(2) The thesis that the two ways are in principle parallel does need some defense, for the initial descriptions Aquinas gives of them in the Summa Theologiae obscure rather than highlight the parallelism. The first lines of his exposition of the “First Way” identify it as an “argument from motion,” from, that is, an effect, that of a mover:
The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another….
(http://dhspriory.org/thomas/summa/FP/FP002.html#FPQ2A3THEP1)
The first lines of his exposition of the “Second Way,” on the other hand, identify it as an “argument from the nature of the efficient cause,” drawing attention to the cause rather than the effect:
The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes.
(Ibid.)
In the post before last, “Gnosis and Noesis Returns: the ‘First Way’ of Aquinas,” in speaking about the critique that Paul Edwards offered of the “Second Way,” I provided a partial justification of the parallelism claim, that of a similarity in focus:
[W]hile the “First Way” has as its focus the change [i.e., in Aquinas’s vocabulary, the motion] that some beings undergo and the causation upon which that change depends, the “Second Way” has as its focus the caused existence of some beings and the causation upon which that existence depends. The causality, however, is in both cases, an “efficient causality.” This is, in the Aristotelian terminology, the activity of an agent, and is thus to be distinguished from, say, “final causality,” the causality of an end or goal. As far as I am aware, the causal series upon which Edwards’ critique bears is, in all relevant respects, exactly similar to Aquinas’s mover/moved series.
(3) Additional justification for the parallelism claim can be found by noting the presence of two sets of two parallel premises. As for the first set of parallel premises, Aquinas, as we have read just above, gives expression to a key premise of his “First Way” in the second sentence of his exposition of the argument. I isolate that premise as:
Some things are in motion.
He does not, in his “Second way,” thus early and explicitly present the analogous premise, i.e.:
Some things are caused.
(For the duration of this post and for the sake of simplicity, I will use “cause” to abbreviate “efficient cause,” “caused” to abbreviate “beings the existence of which depends upon the activity of an efficient cause,” etc. So abbreviating the terms not only makes for easier inspection of the premises and arguments at hand, it also provides the collateral benefit that parallel arguments bearing upon the other modes of causality identified by Aristotle and Aquinas, final, formal, and material causality, are thereby also set forth for logical evaluation in one fell swoop.)
(4) The proposition that some things are caused is, however, hard at work in the argument, as is evident when the argument is fully expressed. This can be seen by rendering explicit the argumentation expressed in a truncated manner in the following sentence, the penultimate of Aquinas’s exposition of the “Second Way”:
But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false.
It quite obviously gives a truncated expression to a sequence of several arguments, one of which is:
If the cause/caused series goes back to infinity, there is no first cause.
If there is no first cause, there is no intermediate cause.
Therefore, if the cause/caused series goes back to infinity, there is no intermediate cause.
The second in the sequence of several arguments is:
If the cause/caused series goes back to infinity, there is no intermediate cause.
If there is no intermediate cause, there is no ultimate cause.
Therefore, if the cause/caused series goes back to infinity, there is no ultimate cause.
The third in the sequence of several arguments is:
If the cause/caused series goes back to infinity, there is no ultimate cause.
If there is no ultimate cause, there is no ultimate effect, i.e., no caused.
Therefore, if the cause/caused series goes back to infinity, there is no ultimate effect, i.e., no caused.
This is the point at which the premise, “Some things are caused,” comes in to play, as the premise in a fourth argument, a double negation argument:
Some things are caused.
Therefore, it is not the case that there is no ultimate effect, i.e., no caused.
That conclusion serves as a premise in a fifth argument, a modus ponendo ponens argument, thus:
If the cause/caused series goes back to infinity, there is no ultimate effect, i.e., no caused.
It is not the case that there is no ultimate effect, i.e., no caused.
Therefore, it is not the case that the cause/caused series goes back to infinity.
Taking stock, we can first see that there is, parallel to the explicitly stated premise of the “First Way,” that:
Some things are in motion.
there is also the implicitly present premise of the “Second Way”:
Some things are caused.
Still taking stock, we can second take note that we have just reviewed Aquinas’s argument that it is not the case that the cause/caused series goes back to infinity.
(5) Now, to turn to the second set of parallel premises: after having presented us, in his exposition of the “First Way,” with the first premise of the argument, Aquinas immediately went on to present us with a second premise of the “First Way,” that:
Whatever is in motion is put in motion by another.
In his exposition of the “Second Way,” however, he does not immediately go on to explicitly state an analogous premise. But it is more than merely plausible that it is implicitly present. First, in his “Third Way,” he denies that anything caused is caused by nothing, telling us that:
Now if this [that at one time there was nothing in existence] were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing.
And, in the “Second Way” itself, he rules out self-causation, saying, “There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself.”
These two theses imply the following proposition, able to serve as a second premise operative in the “Second Way” analogous to the one already seen to be operative in the “First Way”:
Whatever is caused is a caused by another.
(6) Continuing in parallel with the approach I took in “Gnosis and Noesis Returns: the ‘First Way’ of Aquinas,” I will observe here that a proposition like the immediately preceding suggests the question of whether or not, when one thing is the cause of another, the former is itself caused. Given that it either is or is not caused, then:
Either the cause is itself caused by another
or the cause is not itself caused by another.
Now if the latter is the case, then it immediately follows that there is an uncaused cause, in which case Aquinas as would, no doubt too optimistically, go on to say, “this everyone understands to be God.” It seems at least possible, that is, for Aquinas to have had the inference from the latter possibility to the existence of an uncaused cause in mind and thought it to have been sufficiently obvious to not require an explicit exposition. But perhaps not.
(7) At any rate, Aquinas went on to deal with the former, and remaining, possibility, that, again, “the cause is itself caused by another.” And, of course, as it did in the “First Way,” the question arises of whether that cause is itself caused by another. We are thus presented with a cause/caused series that goes back, or regresses, from one cause that is caused by a prior one to that prior one and then to that prior one’s cause, etc. This obviously raises the question of whether or not this series goes back or regresses infinitely.
In “Gnosis and Noesis Returns: the ‘First Way’ of Aquinas,” I noted that the arguments in the “First Way” fell into two, as I called them, movements, the first concluding that the mover/moved series does not go back to infinity and the second that there is an unmoved mover. The parallel series of arguments in the “Second Way” also falls into two such movements, the first concluding that the cause/caused series does not go back to infinity and the second that there is an uncaused cause.
I have, of course, already set forth the series of arguments that constitute the first movement; I did this in making the case, in Section 4 above, that the premise that some things are caused is implicitly present in the “Second Way” and in the process presenting the syllogistically formatted version of Aquinas’s argument that it is not the case that the cause/caused series goes back to infinity. In this section, accordingly, I’ll set forth the second movement.
Now, in presenting the first movement, I introduced and put to use the following premise:
If the cause/caused series goes back to infinity, then there is no first cause.
The reverse can also reasonably be assumed true:
If there is no first cause, then the cause/caused series goes back to infinity.
The sixth argument needed, also a modus ponendo ponens argument, has as it first premise the latter proposition and as its second the last of the conclusions arrived at in the first movement.
If there is no first cause, then the cause/caused series goes back to infinity.
It is not the case that the cause/caused series goes back to infinity.
Therefore, it is not the case that there is no first cause.
The seventh argument is, quite obviously, another case of double negation:
It is not the case that there is no first cause.
Therefore, there is a first cause.
Note that the series of arguments thus far set forth have concluded only that there is a first efficient cause, i.e., there is at least one. They have not ruled out there being many. In what follows, I will use the expression “the first cause under consideration” to refer to the one alone the existence of which the arguments would have, if sound, demonstrated, with no assumption, at least not here, that there is also at most one first efficient cause.
That said, we’re not quite done yet, though the remaining steps are obvious. One, our eighth argument, is:
If the first cause under consideration is caused, then it is posterior to a prior cause.
If the first cause under consideration is posterior to a prior cause, it is not a first cause.
Therefore, if the first cause under consideration is caused, then it is not a first cause.
There is no need to prove that:
The first cause under consideration is a first cause.
The pertinent double negation argument, the tenth, is just as obvious:
The first cause under consideration is a first cause.
Therefore, it is not the case that the first cause under consideration is not a first cause.
Next, eleventh, another modus ponendo ponens:
If the first cause under consideration is caused, then it is not a first cause.
It is not the case that the first cause under consideration is not a first cause.
Therefore, the first cause under consideration is not caused.
Twelfth:
If the first cause under consideration is not caused, then it is an uncaused cause.
The first cause under consideration is not caused.
Therefore, the first cause under consideration is an uncaused cause.
Finally, in setting forth in Gnosis and Noesis Returns: the First Way of Aquinas the “First Way” in syllogistic format, I did not go on to spell out the argument that:
There is a first mover (i.e., the first mover under consideration).
That first mover (the first mover under consideration) is an unmoved mover.
Therefore, there is an unmoved mover.
I probably should have. In this post, however, I will spell out the parallel argument of the “Second Way,” thus:
There is a first cause (i.e., the first cause under consideration).
That first cause (the first cause under consideration) is an uncaused cause.
Therefore, there is an uncaused cause.
(8) It is quite evident that all of the foregoing arguments are perfectly valid. That is, if their premises are true, then their conclusions must also be true. It is not, however, evident that all of the foregoing arguments are perfectly sound. That is, it is not fully evident that all of the premises invoked are true and it is therefore not fully evident that all of the conclusions arrived at are true.
In “A Non-evident and Key Premise of Aquinas’s ‘First Way’”, I recalled Paul Edwards’ critique, by implication of the following premise of Aquinas’s “First Way”:
If there is no first mover, then there are no other, subsequent, movers.
and directly of the parallel premise of his “Second Way”:
If there is no first cause, then there are no intermediate causes.
(The difference between the “other, subsequent” of the former, stemming from Aquinas’s wording in the “First Way,” and the “intermediate” of the latter, stemming from Aquinas’s wording in the “Second Way,” is of no consequence for the current analysis. Subsequent causes, that is, surely include both intermediate and ultimate causes. The exposition I have given of the “First Way” in syllogistic format can easily be revised to make use of the more specific “intermediate causes” and “ultimate causes” instead of the “subsequent” that I in fact used.)
As far as I know Edwards’ critique is still unanswered. In particular, as I pointed out in “A Non-evident and Key Premise of Aquinas’s ‘First Way,’” Edward Feser’s The Last Superstition. A Refutation of the New Atheism (South Bend, Indiana: St. Augustine’s Press, 2008) does not mention it, much less reply to it.