The statement if youth knew and age could refers to the possibility of what things could be if the young knew the truths of life and were wise and if the old could be more strong and do what is required even in old age. The statement seems to suggest that such things are only utopic dreams and not actually possible, since the youth lack wisdom and the old lack physical strength. In the new age however this seems very much possible. First, the youth of today is far more wisened and second, the old far more young.
There was a time when at 40 one felt like a really old man with grandchildren and failing health, a time more appropriate for the recommended 'vanaprastha' as per old hindu customs. It was time to let your son be the head of the joint family and take over the reigns of the physically strenuous duties of maintaining the household. Even though one did not go out into the jungle, one simply relaxed and used his wisdom to guide the new head of the family. Those were ofcourse times when a lot of physical labour was required to achieve anything. People traveled on foot, did not have the comforts of modern day living, could not do business right from the home via the phone or internet, etc.
Now science and medicine have advanced enough to make life absolutely sedentary and easy on the physique. Longevity and vigour have dramatically improved. At forty, one manages to marry and only slightly settle into some kind of life. Children are still school going and in no way ready to take over the reigns. In fact the saying 'life starts at forty' seems more appropriate and retirement isn't even an option. Yes government servants do have a retirement age, but that is a forced decision rather than an optional one or a necessary one. Things like retirement ages fixed by governments are very much dependant on political and other social factors like availability of jobs etc. And people continue in similar fields or do something new even after retirement. Even in sports people no longer retire. They may not play any more, but they either start coaching or doing commentaries or open sports institutes. Nowadays, the youth wings of various parties have leaders the age of forty, a clear signal towards what is called youth today.
On the other hand, is the youth of today, very mature and responsible. The exposure that they go through and the pressure to excel in this very competitive age has made them more mature than they were ever. Of course in early ages the youth of today were considered adults and had to take the responsibilities of the whole family and was already a parent in his teens. The definition of youth has changed since, and now means people in their twenties and early thirties. The 20th century defined the youth as those, that had to educate themselves on emerging streams of knowledge and were exonerated from demanding jobs and responsibilities. But this padding did not last in the 21st century when younger and younger people started taking charge of situations and the traditionally old sectors like management were taken over by the youth. The media coupled with other forces have lead the children of today to be more informed, more aggressive and more willing to take over responsibilities. Earlier there were limited fields where young people achieved, one being sports, but now we see young people achieving everywhere. We even have many young people as Union Ministers. Earlier it was said, only years of long practice made you perfect enough in any field specially in the fine arts, but now we have newer and younger artists taking over in a more pressurizing environment and doing very well. One of the reasons for this success could well be due to a large and ever growing segment of young consumers who know their minds. A new kind of maturity seems have taken over the youth of today. In fact children too seem to be very much mature and learn to fend for themselves in these pressure driven times.
The above statement also implies that young people are more energetic and over enthusiastic and the old more balanced and patient but at the same time, may lack the drive to change things. The youth in their enthusiasm overlook some finer details and jeopardize the journey; and the old, being overcautious, miss the bus. It further implies that if only the youth knew more balance and the old, more adventure, great things could be achieved. And this is the balance that our own government has tried to achieve through the civil services, which puts young Turk's at the head of departments full of older and experienced people who can constantly guide them and ring the warning bells; while the young ones with their fresh insights and enthusiasm can give shape to a new
Having seen that an aged person now is not a man of 40 but more suitably of 60, and a young man is not only a man in his 20's but well may be nearer 40, there has occurred an overlapping of the young and the old. This obviously means an admixture of the old and the young. This potent mixture has all the capabilities of fulfilling mankind's dreams, and we are surely headed towards the right direction. There is, however, still talk of things like generation gap, but this gap is not only between the old and the young. Longevity has given rise now to the gap between the very young, the mature and the old, and the idea is very well portrayed by the veteran filmmaker Mr. Raj Kapoor, in his film 'Kal Aaj Aur Kal'. A greater openness and the overlapping of youth and old has lead to a greater understanding of things. We are surely heading towards a balance of mind in the young and a feeling of adventure in the old, and therefore it's no longer 'if we could', but 'we shall'. We know and we can.