This is what my wife and I teach our 12 kids at home so when they go into the world, they are the head and not the tail.

Three terms to consider:
pre-modernity - Christian consensus.
modernity - rationalistic humanism/rejection of scholasticism.
postmodernity - existential systems

In pre-modernity if you stood in the street of any city and said, "The Bible says this is right," then everyone (including the non-Christian) listening would have thought by default that the opposite then of what the Bible says is right, is therefore wrong. People here reasoned along the basic Christian presuppositions.

Modernity was a rejection of the scholastic tradition with the emphasis being placed on the human intellect alone (humanism). Man is seen here as the measure of all things because knowledge value and meaning are derived from man alone. Proponents of this system eventually realised the insufficiencey of their system because of the finite nature of man. Modernity is symbolised by the 'industrial' error where advances in technology ushered in this humanistic framework. When people studied this system they found that it reduced people to a zero or accident of evolution, machines as Frued would say or merely chemicals as Marques de Sade said. Postmodernism was bourn out of a rejection for this loss of mans' uniquesness. If the modernist had failed applying their rationalistic methodology, then they were going to look in the area of the non-rational. if you preached to these people, they would understand your message but reject it in favour of a more intellectual system that can be explained.

Postmodernism is mans' attempt to answer the two basic philosophic questions of metaphysics and of morals in the area of the non-rational (that which cannot be explained rationally). Who am I and where did I come from for example or who am I and what is wrong with me. Actually the father of all existential philosophy was a Christian by the name of Sorens Kierkergaard. He would not be pleased with what developed from his work however he did become the father of existential philosophy. if you preached to these people, they would have no idea what you are talking about.

So what does this all mean today. Well the postmodern concept for truth is the opposite of that of the Christian. Our ability to say a Rose is beautiful only has meaning if we can say that the Rose can also be not beautiful. Beautiful has meaning here. God is, or God is not for example. Two opposites where one is right and the other is wrong providing us with a certainty of knowledge.

Postmodernism is epitomised by its concept of truth where the two opposites find a unity in synthesis. A conflict resolution process that never ends. Here certainty of knowledge is not possible because it is the process and not the solution that counts here. So here there are no categories for knowing anything with certainty. So whether a person is heterosexual or homosexual or bald or not bald is of no relavance in the postmodern context. In this context truth is what 'I' the individual say it is.

Now the Christian consensus gave us certainty of knowledge based upon God's propositional verbalised revelation the Bible. We have a 'yes' and 'no' methodology but with postmodernism we have a 'yes' and 'yes' methodology. This means that people think in a contrary way to the way God designed us to be.

If our modern world in which Britney lives in thinks in terms of 'yes' and 'yes' then man as we understand him to be according to the Bible is dead. God is dead man is dead value and meaning are also dead. This is where our non-Christian world begin.

For us the Christian not to understand this would put the non-Christian in a very compromising position and they wouldn't even know. When we talk to our non-Christian world we must talk to their intellect and their intellects function upon a different framework to us the Christian. if we fail to understand this, we will be largely talking to ourselves.

Rather than a mid quater crisis, I would say the problem is rather the two basic philosophic questions that confront every man and woman. At the well in Shechem with the Samritan woman the questions were the same. With the man from Gadarene the questions were the same. With the men on the road to Emmaus the questions are the same.

In our 21st century post-Christian world the questions are the same. The problem is as Jesus said, the labourers do not understand what confronts them as a totally monolithic post-Christian culture. Jesus said we are to resist the psirit of the world in our time. But what form does the spirit of the world take in our 21st century? Man has gone from 'yes' and 'no' which gave us certainty of knowledge to 'yes' and 'yes' which gives us absolutely nothing. Hence humanity treats people as it world view dictates.

God Bless big time

One thing I learnt in my studies of Youth & Community Work is that the equivalent of a mid-life crisis will be a recurring event every 7 years if we don't solve the underlying issue. It starts at 21.

The founder of Logotherapy and the "Third Viennese School" of Psychotherapy Victor Frankl once stated that life is about finding meaning.
If we can find something to live for – if we can find some meaning to put at the center of our lives – even the worst kind of suffering becomes bearable.
The problem comes when we realise the meaning we think we are living for is meaningless, or when we are living for something that is a means and not the end.

"Don't aim at success - the more you aim at it and make it a target, the more you are going to miss it. For success, like happiness, cannot be pursued; it must ensue, and it only does so as the unintended side effect of one's personal dedication to a cause greater than oneself or as the by product of one's surrender to a person other than oneself. Happiness must happen, and the same holds for success: you have to let it happen by not caring about it. I want you to listen to what your conscience commands you to do and go on to carry it out to the best of your knowledge. Then you will live to see that in the long run - in the long run, I say! - success will follow you precisely because you had forgotten to think of it" (from the preface of Victor Frankl's book Man's Search for Meaning)

It can only be done by aiming for something else.
For most westerners, this is how life is lived. This means that every seven years or so, we come to a point of wondering what it's all about, and whether we're doing what we should be. This actually happens to a different extent for people who live with a purpose too, if that purpose isn't what God created them for. We're made that intricately that we can be doing amazing stuff with our lives, even as Christians, but still know deep down that we're off track from what God created us to do.
So what often happens is that the first time round, people try to find this meaning. They seem to get it, and life goes on again. But they may have missed the mark. So the problem of purpose comes up again. Often around seven years later. This is often called the "seven year itch" in marriage, because the meaning is misconstrued as the possibility of having chosen the wrong spouse.

So what's the remedy? Listen to God, be open to His direction, and stick by what you know to be universally true. (like sticking to one husband/wife for your entire life)

I agree with Kim, Crises pop up at all stages of life, though being a 20 something myself, I look around at my peers today and I'm not surprised that there is such a phrase as Quarter Life Crisis... Especially with the staggering figures of Suicide with Males in their 20's, More young people being diagnosed with Clinical Depression to small things like the amount of Uni Drop Outs.

The 20's ain't no cup of tea in the Noughties, there's such a tension from being a child to being an Adult. And with a constant message from the world that YOU ARE THE MOST IMPORTANT THING and that SUCCESS IS IMPORTANT, If you haven't found yourself by 25 and made a success, saved money, got a Morgage (like the baby boomers seemed capable of doing in the 60's 70's) then perhaps you aren't the best you can be. You've failed. TALK ABOUT PRESSURE!

As a Christian I'm blessed to know that God is the most important thing in my life and that I find my value in him and him alone, but even then being bombarded with the pressure of the World, sometimes it's easy to believe the lies that the world send out that you have no self worth unless you fit the mould. I suppose that’s going to be that Struggle living in a Sinful world.

I understand that in the world we live in - you can be having a crises at ANY age - teens, mid-20s, mid-40s, 60s etc. But I think this is just a 'band-wagon' that someone is riding to write and sell a book.

I think rather than crises you have 'decisions' to make when you're 25. If you're married you might be thinking about having children or buying a home, if you're single you could be considering career paths, travel, marriage...

At 25 I had decisions to make about career and whether or not to move to Sydney to further it. It was hard, but not a crises as such, just life. 10 years on I have decisions to make about buying a home, looking after my health for the future etc.

Throughout life we will always have life decisions to make, some are much harder than others, but by taking these to God - walking and trusting him with every step you take, you don't have to fall into a crises.