The Second Way in Syllogistic Form

The Second Way in Syllogistic Form

I. The Text (ST I.2.3c):

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. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. 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. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.

II. Summary: A is caused by B, which is caused by C, which is caused by D... We need a first, uncaused cause.

III. The Argument in Syllogistic Format: 

P1: There is an order of efficient causes.                                                                                                      

[P2: If there is an order of efficient causes, then either (a) a thing causes itself; or (b) a thing is caused by another.]

P3: It is impossible for a thing to be the efficient cause of itself.

[P4: If a thing is caused by another, then either (c) efficient causes go on to infinity; or (d) there is a first efficient cause.]

P5: Now in efficient causes it is not possible to go on to infinity.

C: Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.

Defense of P1: In the world of sense we find this to be the case.

Defense of P3:  for so it would be prior to itself, which is impossible.

Defense of P5: because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But all of this is plainly false. 

IV. The Formal Structure of the Argument:

P1: o

[P2: o ---> (a V b)]

P3: ~a

[P4: b ---> (c V d)]

P5: ~c

C: Therefore, d.

V. See also:

The First Way in Syllogistic Form.

The Third Way in Syllogistic Form.

The Fourth Way in Syllogistic Form.

The Fifth Way in Syllogistic Form.