What does 'by the foolishness of preaching to save them that believe' mean?

Preaching seems foolish to the world, and the idea that God could save through preaching must seem foolish to some.

Paul wrote, in I Corinthians 1:21
For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.

There are some people who read 'preach' in the Bible who think it refers to a pastor behind a pulpit preaching a weekly sermon of about 45 minutes or so. But that interpretation can lead to some rather odd interpretations of a number of verses. This is one of them.

Does anyone believe that we are incrementally saved by hearing Sunday sermons? Do sermons impart micro-doses of salvific grace to the soul until finally one is saved?

It is useful to realize that generally, when 'preach' is used in scripture, it is used of proclaiming the Gospel to those who haven't believed it yet, in evangelistic contexts. It depends on the translation and what words the translators use in a given context, but this is the general use of 'preach.' In modern times, we use 'preach' to refer to teaching or exhortation activities in church, but it is helpful to be careful not to read that back into context.

We should also keep this in mind when Paul writes that they that preach the Gospel should live of the Gospel. Much of the activity we see Paul engaged in in Acts was proclaiming Christ in synagogues or other venues like the marketplace, introducing the Gospel to those who were not yet a part of the church. Paul was engaged in evangelistic preaching-- preaching.

I Corinthians chapter 1

[18] For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.
[19] For it is written, I will destroy the wisdom of the wise, and will bring to nothing the understanding of the prudent.
[20] Where is the wise? where is the scribe? where is the disputer of this world? hath not God made foolish the wisdom of this world?
[21] For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.
[22] For the Jews require a sign, and the Greeks seek after wisdom:
[23] But we preach Christ crucified, unto the Jews a stumblingblock, and unto the Greeks foolishness;
[24] But unto them which are called, both Jews and Greeks, Christ the power of God, and the wisdom of God.
[25] Because the foolishness of God is wiser than men; and the weakness of God is stronger than men.

I believe that the answer to your question is found in verse 22.

"The Jews require a sign" or, generally speaking, some sort of outward display of God's power.

Does Christ hanging upon a cross seem like "a powerful sign"?

It is, but not in the manner that they were seeking.

The same principle applies to the Greeks to whom Paul was primarily speaking in that "the Greeks seek after wisdom".

Does Christ hanging upon a cross seem "wise" to those who basically went about philosophizing all of the time? They were also into all sorts of powerful Greek "gods" themselves and sporting events like our modern-day Olympics.

To people such as these, Christ hanging from a cross doesn't seem "wise", but it is.

When Paul said "the world by wisdom knew not God", I believe that he was referring to the type of Satanic wisdom that entered into the world when Adam and Eve partook of the forbidden fruit that came from "a tree to be desired to make one wise" (Genesis 3:6).

Seeing how the world knew not God via this type of wisdom, "it pleased God by the foolishness of preaching to save them that believe."

it's just enough foolishness to hit the ears of the unbeliever where the Holy Spirit can then work on their heart and mind.

quite amazing how simple hearing Jesus loves you and He died for you is more than enough for the Spirit of God to kick the doors of unbelief down.

The foolishness of preaching" is more about the idea that the crucifixion of Christ could not possibly be the means of salvation. It appears foolish to the natural man that the sufferings and death of Christ actually opened the door to Heaven, and that He rose again for our justification.

It was unrealistic to think responses would focus narrowly on the issue of what 'preaching' means in the context of the verse quoted in the OP or in other NT passages.

Agree.

Probably, but not I. The thief on the cross certainly didn't attend too many church services.

The blood is applied at the moment we first believe, and it washes us white as snow. I believe that sanctification is the term we use to describe progressive growth.
We are justified the moment we first believe.

Here is the foolishness of the cross.

Deuteronomy 24:16 The fathers shall not be put to death for the children, neither shall the children be put to death for the fathers: every man shall be put to death for his own sin.

in the pulpit commentary;

1Co 1:21
In the wisdom of God; that is, as a part of his Divine economy. The world through its wisdom knew not God. These words might be written as an epitaph on the tomb of ancient philosophy, and of modern philosophy and science so far as it assumes an anti-Christian form (Luk 10:21). Human wisdom, when it relies solely on itself, may "feel after God," but hardly find him (Act 17:26, Act 17:27). Through the foolishness of the preaching. This is a mis-translation. It would require keruxeos, not kerugmatos. It should be by the foolishness (as men esteemed it) of the thing preached.

John Gill connemtary;
1 Corinthians 1:21
For after that in the wisdom of God,.... These words contain a reason proving the infatuation of men, with respect to "the wisdom of God"; by which may be meant either Christ, who is the wisdom of God, was in the world, and yet the world of the Jews, and their chief Rabbins among them, with all their wisdom, neither knew him, nor God his Father; or the Gospel, which is also so called, and though this was come, both into the Jewish and Gentile world, yet neither of them, by their natural wisdom, knew the God of grace, so manifestly revealed in it; or rather the works of creation, in which there is such a visible display of the wisdom of God: yet "the world by wisdom knew not God"; the author of them: the Gentiles knew him not in any spiritual and saving manner, as in Christ, or the God of all grace; yea, they knew him not as the God of nature to be the one, only, true God; they knew him not so as to glorify him as God, or to worship him in a right way and manner: wherefore,
it pleased God by the foolishness of preaching to save them that believe; it was his purpose and decree within himself; it was his sovereign good will and pleasure; it was what he, without any motion from, or merit in the creature, resolved of himself from all eternity that he would "save", not the wise man, the Scribe, the disputer of this world, the rationalist, the talker, nor the worker, but "them that believe" in his Son; that look unto him, venture on him, and commit the care and keeping of their souls to him, however weak, mean, and despicable they may otherwise be; or whether they believe with a weak, or a strong faith, so be it, it is but true: the Ethiopic version reads, "that believe in this foolish doctrine"; and this he determined to do, and did, "by the foolishness of preaching"; or by that sort of preaching, which both for the matter of it, Christ, that itself, and the manner of it, the world reckons foolishness; and which are the things of the Father's grace in election, of the Son's grace in redemption, and the Spirit's in regeneration: so the wise men of the world, with all their wisdom, are left ignorant of God, and perish in their sins, whilst the Gospel they despise is the power of God unto salvation to all that believe in Christ; this, through efficacious grace, becomes the means of regenerating and quickening men, showing them their need of salvation, and where it is, and of working faith in them to look to Christ for it.

The foolishness of preaching is that the preacher has ZERO ability to prove his case [unlike the scientist or the philosopher, the wise men of the world]

We make enormous claims, incredible statements about the forgiveness of sins at the cross, healing and deliverance. The power of the new birth.

Then after all this we must throw the whole thing over to God to demonstrate by His Spirit that these things are true.