For an Informed Love of God
First class conditional sentences are formed with a protasis (the “if” clause) with εἰ and the indicative (any tense). Their basic meaning is to say that if such-and-such is true (and we will accept the truth of the protasis for the sake of the argument), then such-and-such will occur.
Of course, that does not mean the protasis actually is true. It could be a lie, or it could just not be true. In fact, the second class conditional sentence (“condition contrary to fact” it is also called) is identical in form to the first (except that the verb in the protasis is past time) and the protasis is clearly false. “If you believed Moses, you would believe me, for he wrote about me” (Jn 5:46). They clearly do not believe Moses.
I have often heard it argued that you should translate the εἰ of the protasis as “since” and not “if” since the protasis is assumed to be true. There certainly are verses in which the use of “if” adds an apparent element of question that is not appropriate for what is being said. Satan says, “If you are the Son of God [εἰ υἱὸς εἶ τοῦ θεοῦ], tell this stone to become bread” (Luke 4:3). There was no question in Satan’s mind who Jesus was.
Wallace argues strongly against this practice, saying that it over-translates εἰ, saying more than εἰ actually says (pp. 692f.). Greek has a word for “since,” you don’t know if the speaker “would actually affirm the truth of the protasis,” and sometimes this construction is used with a rhetorical force that is removed by “since.”
I came across a great example of this latter argument. When you look at 1 Cor 15:12 out of context, it seems a candidate for “since.” “Now if Christ is proclaimed as raised from the dead, how can some of you say that there is no resurrection of the dead?” There is no question that “Christ is proclaimed as raised from the dead,” so why not translate “since Christ is proclaimed as raised from the dead”?
But look at the next two verses. “But if there is no resurrection of the dead, not even Christ has been raised” (1 Cor 15:13). “And if Christ has not been raised, then our proclamation is groundless, and your faith is to no purpose” (1 Cor 15:14).
Here is a rhetorically powerful triad of confessions that Paul is calling the Corinthians to affirm (even though the second is in reverse).
The use of “if” in this triad calls for an affirmation of faith on the part of the reader, an affirmation that they believe Christ has been raised from the dead, that there is a resurrection, and that Christ has been raised.
“Since” would destroy the rhetorical strength of Paul’s statements.