Predestination

In order to understand what Paul meant by predestination, let's first consider the design of Paul's argument in the Epistle to the Romans.

In chapter 1, Paul described the sinfulness of the Gentiles who didn't have the Law.

In chapter 2, he said the Jews also were sinful, even though they had the Law.

In chapter 3, Paul said that although being Jewish had some advantages, being Jewish couldn't actually save a person, and neither could keeping Moses' Law - salvation can be received only through faith in Jesus - irrespective of whether we are Jew or Gentile.

In chapter 4, Paul proves his premise that salvation is received only through faith in Jesus from the life of Abraham.

In chapter 5, he goes into more detail about why it's only faith in Jesus - and not Jewishness, or keeping the Law - that saves (irrespective of whether a person is Jew or Gentile).

Now in chapter 6, he begins to anticipate and address a likely objection or question about his message of grace and faith (as opposed to Law-keeping): Doesn't this message encourage sin? No - it empowers us to live holy!

This message was controversial and obviously attracted persecution and hardship against the believers. So Paul comforted them by saying that their hardships would have a good outcome (Romans 8:28) seeing they (the believers) are them that love God (even though their Jewish persecutors may not have thought the believers were lovers of God) - them who are called according to His purpose (even though their persecutors did not think the Gospel was a genuine plan of God).