Of the different world views presented in As You Like It, is Jaques' (Duke Senior's friend's) an acceptable one and why or why not?
Jaques' world view is meant to be the guiding light in many respects, yet in many other respects, it is meant to be the one to escape from. Perhaps it is more accurate to state that it is also meant to be the one that shows the logical outcome of a negative perspective on humans' situation in life.
As an example of this unacceptable world view held by Jaques, Touchstone talks about humans' brief time in life and it is meant to arouse humor as life is viewed by the listener (in this case, Jaques) through the eyes of wit. Yes, sudden ends in death after brief flowerings of youth are the reality, but wit can make it remote, put it in perspective and add a dose of humor.
A fool, a fool! I met a fool i' the forest,
[Touchstone] Says very wisely, 'It is ten o'clock:
Thus we may see,' quoth he, 'how the world wags:
And so, from hour to hour, we ripe and ripe,
And then, from hour to hour, we rot and rot;
And thereby hangs a tale.' When I did hear
The motley fool thus moral on the time,
My lungs began to crow like chanticleer,...
Jaques talks about the same thing--humans' brief time upon the stage of life (a metaphor borrowed from Duke Senior)--and it is meant to unleash melancholy and regret that so little is accomplished and that the unhappy, unpleasant end comes so soon and so tragically. Jaques sees into the nearness of the continually approaching end and makes it near at hand, ever present, painfully real.
All the world's a stage,
And all the men and women merely players:
... Last scene of all,
Sans teeth, sans eyes, sans taste, sans everything.
According to the Renaissance concept of mimesis (i.e., divine truths mimicked in poetry with examples of all possibilities of the truth so humans might embrace the divine principle of the truth), Shakespeare offers both perspectives on life to illustrate that melancholy and despair can lead to a distressed life while wit and a joyful perspective can lead to a happy life. Thus Shakespeare presents Jaques' worldview as an unacceptable one, then sends him off to a life of contemplation:
... So, to your pleasures:
I am for other than for dancing measures.