Jonathan Edwards masterfully argues that it is necessary that God determined that at least one individual would be saved, or else there would have been the risk that Jesus work would have been done in vain. The implication of this argument is of course that once you have accepted that at least one person was chose effectually by God to be saved, it is surely easy to believe that all Chrisitans were in fact chosen by God before the foundation of the world without anything in us cause him to be pleased with us.
If God ever determined in the general, that some of mankind should certainly be saved, and did not leave it altogether undetermined, whether ever so much as one soul of all mankind should believe in Christ, it must be that he determined that some particular persons should certainly believe in him. For it is certain, that if he has left it undetermined concerning this and that and the other person, whether ever he should believe or not, and so of every particular person in the world; then there is no necessity at all, that this or that or any particular person in the world should ever be saved by Christ, for matter of any determination of God’s. So that, though God sent his Son into the world, yet the matter was left altogether undetermined by God, whether ever any person should be saved by him; and there was all this ado about Christ’s birth, death, resurrection, ascension and sitting at God’s right hand, when it was not as yet determined whether he should ever redeem one soul, or have any mediatorial kingdom at all. – Jonathan Edwards , The “Miscellanies”: (Entry Nos. a–z, aa–zz, 1–500) (WJE Online Vol. 13) , Ed. Harry S. Stout, page 233-234