What is the significance of Jaques and Touchstone in Shakespeare's As You Like It?

Jaques and Touchstone have similar purposes in one regard
in As You Like It, but have very different purposes in another
regard. First, they have similar purposes in that, though of different backgrounds and
stations in life, both serve as diversion and amusement for the principle characters
attached to them. Jaques, though a lord in exile with Duke Senior, diverts the Duke with
his melancholy and with his wordy witticisms--the wit of some of which he may be
unaware.

On the other hand, though Touchstone similarly
provides amusement and the diversion from word play for the royals he serves (first at
court and still in the Forest of Arden), he has always had the lowly station the court
jester in motley (multi-colored clothes) as the Shakespearean Fool. The major difference
between the Shakespearean Fool and Clown, aside from being urban and rural,
respectively, is that the Fool intends to make word play and be witty whereas the Clown
does so unintentionally by accident rather than by choice. By this part of the
definition, Jaques might reasonably considered to be fulfilling the office of accidental
country Clown for Duke Senior's group of pastoral
exiles.

The major difference in their purposes is that
Touchstone, whether he wants to or not, whether by design or by accident, reflects back
the worth and truth, if there be any, of the person conversing with him, whereas Jaques
provides an alternate point of view about the pastoral life of the exiles in Arden.
First, a touchstone (a geologic stone) is so named because when gold or silver is rubbed
on it a distinctive mark is left behind that identifies the true nature of the metal.
This was quite important in eras where metals of inferior origins were passed off as
gold and silver. Similarly, Touchstone's conversations with other characters display the
worth of their points of view and their beliefs. A good example is Touchstone's
conversation with the old shepherd, Corin, in which the truth and sincere simplicity of
Corin's believes is made evident since Touchstone can't offer an opinion, witty or
otherwise, that can stand up to Corin's statements.

Jaques'
melancholy spirit and gloomy conversation, on the other hand, stand as alternatives to
the prevalent points of view in the play. All the other characters, except perhaps
Touchstone, are all delighted with the pastoral life and the life of simplicity in
Arden, which includes the deposed Duke Senior and his exiled lords. However, as a good
example of his purpose, Jaques disagrees with the exiles' belief that the forest
creatures, such as the deer, are there to provide food for them and that the death of a
deer is a sad but necessary event. Jaques presses the point that the exiles are exerting
the same rule of order that drove them into exile, the law of "right by power." In the
end, Jaques yields to his view of life and chooses to explore exiling himself into a
truly pastoral monastic life.