The purpose of swift's satires is to effect change mock weakness entertain all of the above

All of the above.

Explanation:

The original title Swift's Satire is" A Modest Proposal For preventing the Children of Poor People From being a Burthen to Their Parents or Country, and For making them Beneficial to the Publick" which is commonly know as "A Modest Proposal". In his satire, Swift demands an effect of change also, it is a mockery also on the prevailing corruption in the society.

A satire is the rhetorical device used in a text to bring to the light the follies and corruption that is dominating the society. The writer is able to do this with the help creating of humor and irony in an exaggerated manner.

So, the purpose of Swift's satire was, first, to effect change, second, to mock the weakness of the Government or their inability to bring justice to Irish people, and third, to entertain, this was done by Swift by writing a satire, which have elements of humor and irony in it.