Oh, what a difference a single letter can make!
There is an interesting textual issue at the end of John 20. John writes, “these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name” (20:31 ESV, emphasis mine).
As stated in the sermon, there are two competing manuscript traditions. One has pisteu,the, a present subjunctive, which some say should be interpreted “that you may continue to believe.” Other manuscripts have pisteu,shte (the only difference is that one little s in there), which is an aorist subjunctive (aorist is the tense that describes “an undefined action that normally occurs in the past”; Mounce, Biblical Greek, 3rd ed., pg. 195). Some think that should be interpreted, “that you may come to believe.”
In other words, the divide can be summarized like this:
|Verb Tense & Mood||Present Subjunctive||Aorist Subjunctive|
|Interpretive Translation||“that you may continue to believe”||“that you may come to believe”|
|Audience of John’s Gospel||Believers||Unbelievers|
However, a sharp distinction need not be made between the present and aorist verbs. John has a habit of using synonyms with no distinguishable meaning (check out the sermon next week for an example of this). The same is true with how he uses the aorist and present tense of the verb “to believe.” Look at these following examples (all examples in ESV):
John 1:7 He came as a witness, to bear witness about the light, that all might believe through him.
This use of the verb pisteuō (πιστεύω) is aorist, and it refers to someone coming to salvation. So, initial faith.
John 14:29 And now I have told you before it takes place, so that when it does take place you may believe.
This is also an aorist. Jesus is speaking here about ascending to the Father. At the time of the ascension, the disciples certainly already had faith in Jesus. So this aorist is speaking of their ongoing faith.
John 17:21 that they may all be one, just as you, Father, are in me, and I in you, that they also may be in us, so that the world may believe that you have sent me.
This time we have a present tense. This present tense speaks of the world believing, and in John, the world is almost always representing the unbelieving people on earth. So if the world believed, it would be an example of initial faith.
John 16:30 Now we know that you know all things and do not need anyone to question you; this is why we believe that you came from God.”
Here is another present tense. This is talking about ongoing faith, because by this time the disciples were already said to have believed in Jesus (see 6:69). Certainly this belief developed and grew over time, but it is unlikely that this here in John 16:30 is the moment of conversion for the disciples.
To summarize, we have examples of the aorist being used for both initial and ongoing faith, and examples of the present used for both initial and ongoing faith. More examples could be added (see Kruse, John, 380). But the point is, even if we could be certain which verb tense John 20:31 used originally, the meaning would still need to be decided by context. Verb tense alone would not determine whether the purpose of John’s Gospel was for believers or unbelievers.
Personally, I think a better case can be made that the Gospel was primarily written with unbelievers in mind. This is not to say that we believers don’t benefit from it, but it simply indicates that unbelievers were the primary target audience.