"And according to Paul's custom, he went to them, and for three Sabbaths reasoned with them from the Scriptures, explaining and giving evidence that the Christ had to suffer and rise again from the dead, and saying, 'This Jesus whom I am proclaiming to you is the Christ'" (Acts 17:2-3)
These verses are talking about Paul's teaching in the synagogue in Thessalonica. He came with the message that Jesus was the Messiah who had been prophesied of in the Old Testament.
Notice how Paul taught this message. He did not simply state his premise that Jesus was the Christ and therefore had to suffer and rise again. He explained and gave evidence. His explanations and evidence were from the Scriptures.
Paul's main point was true: the Christ had to suffer, die, and rise again and that Jesus was the Christ. But Paul did not expect them to accept this simply because he said it. He pointed them to the Scriptures and reasoned from them. He later wrote to the ones here who accepted his message, "we also constantly thank God that when you received the word of God which you heard from us, you accepted it not as the word of men, but for what it really is, the word of God" (1 Thessalonians 2:13). They could accept it as the word of God because they were shown that it was the word of God.
We must teach in the same way today. Never expect someone to accept a point you make, even if it's true, simply because you say it. Reason from the Scriptures. Explain and give evidence why the point is true. Our aim is to bring people to faith. Faith, the type of faith that saves, does not come by hearing what men say, but hearing that comes "by the word of God" (Romans 10:17).