PJ and other Daxia: self-petition I-140

For I-140 self petition, can I fill it in myself? I was confused by the following sentences from uscis.gov:
Form I-140: Purpose of Form :
To petition for an alien worker to become a permanent resident in the United States. This form is filed on behalf of an alien, and not by the alien.

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• 回複：PJ and other Daxia: self-petition I-140 -pjiang- ♀ (174 bytes) () 02/15/2010 postreply 11:43:54

• 回複：回複：PJ and other Daxia: self-petition I-140 -chircyhu- ♀ (29 bytes) () 02/15/2010 postreply 18:20:30