In 12 Coritnhtians Paul is using
... of my weaknesses. (ESV) / ... ἐν ταῖς ἀσθενείαις (NESTLE1904 GNT) / ... ἐν ταῖς ἀσθενείαις (SBLGNT)
The Greek word ἀσθένεια / asthéneia is formed with ἀ privativum from σθένος sthenos and it means weakness, infirmity, illness, impotence of different kinds. It is used as referring to the whole human being, yet it can also refer to a special form of bodily weakness.
In the NT writings it is hardly ever used of purely physical weakness. Most frequently it is used in the comprehensive sense of the whole human:
This was to fulfill what was spoken by the prophet Isaiah: “He took
our illnesses [τὰς ἀσθενείας] and bore our diseases.” See Isaiah 53:4.
But now even more the report about him went abroad, and great crowds
gathered to hear him and to be healed of their infirmities [ἀπὸ τῶν
In Luke 5:15, ἀσθενείας is about physical weaknesses due to various diseases of the human body. Yet in Matthew 8:17 it seems to be something more than a mere bodily weakness. Is in Matthew 8:17 this ἀσθενείας the result of these diseases?
In 1 Corinthians 11:30, Paul is interestingly using a synonym:
1 Corinthians 11:30
That is why many of you are weak (ἀσθενεῖς) and ill (ἄρρωστοι), and
some have died.
Here we have "weak" (ἀσθενεῖς) and "ill" (ἄρρωστοι). As they are used together, we can think that there is an important difference between them. So, ἀσθενεῖς would refer to those suffering from weakness of any kind, whereas the other would indicate actual physical sickness, just like in Matthew 14:14:
When he went ashore he saw a great crowd, and he had compassion on
them and healed their sick [τοὺς ἀρρώστους αὐτῶν].
See also in Mark 6:5, the same word for just "sick".
Can we thus say that ἀσθένεια may refer rather to the symptoms of sickness, whatever that may be?
Yet in Romans, Paul seems to go into a rather theological side of the matter:
Likewise the Spirit helps us in our weakness... (ESV)
That was a theological assertion, so weakness would go beyond a medical understanding.
I am speaking in human terms because of the weakness of your flesh.
Here, “the weakness of your flesh” is another theological assertion revealing the resident weakness of the flesh due to sin.
1 Corinthians 15:43
It is sown in dishonor; it is raised in glory. It is sown in weakness;
it is raised in power. (ESV)
Here, the weakness of the body is contrasted to the power of the spirit - another theological assertion.
In places like 2 Corinthians 12, Paul is using ἀσθένεια as a general state of the human being, a state originated by the Adamic sin and manifested into his body. However, the power of God is made manifest through these weaknesses (Rom. 4:20; Eph. 6:10; Phil. 4:13; 1 Tim. 1:12; 2 Tim. 2:1; 4:17), as Christ’s death and resurrection is providing the means for redemption. Then why the body is still weak, still affected by ἀσθενείας? I think this is one of the things that Paul is realizing in 2 Corinthians 12:5. Paul has particularly in view the religious and moral weakness of the human being as a whole, body and spirit. And there is a paradox here, as Paul is realizing a second thing, that these weaknesses can also be the place where the divine power is revealed on earth.
Yes, it might be that Paul was suffering himself of a disease (2 Corinthians 12:7-9), but even so, I find fascinating what Paul is making out of this.
Therefore Paul is seeing this paradox, that these weaknesses are a part of the fallen human nature thorough which the divine power is working our redemption. So as they are not just sin per se and since they are not just flesh, they are not exactly something to be overcome. They are rather something to be recognized as such and they can become an occasion, a circumstance for the power of God to become manifest (like in 2 Corinthians 12) and as a consequence of this, an opportunity for the human to acknowledge this work of God into his life and to confess with joy about it, just like Paul.