"A group of Epicurean and Stoic philosophers began to dispute with him. Some of them asked, 'What is this babbler trying to say?' Others remarked, 'He seems to be advocating foreign gods.' They said this because Paul was preaching the good news about Jesus and the resurrection." NIV translation
Now Athens was famous for their people meeting and debating all of the latest ideas (philosophies). When Paul spoke of Jesus and His resurrection, that brought him into direct conflict with the latest Greek philosophies. The Epicureans met in a place called "the Garden" in Athens and they believed that pleasure was the supreme god and that the life we see here is all there is. Today this is still practiced in what is commonly called Hedonism and the idea is "if it feels good, do it". The other main group that opposed Paul was the Stoics which were the direct opposite of the Epicureans. They believe that virtue is sufficient for happiness and took pride in avoiding pleasure. When Paul spoke of the resurrection, the Epicureans didn't like it and, when he spoke of Jesus being the key to happiness, the Stoics didn't like it.
"Then they took him and brought him to a meeting of the Aeropagus, where they said to him, 'May we know what this new teaching is that you are presenting? You are bringing some strange ideas to our ears, and we want to know what they mean.' (All the Athenians and the foreigners who lived there spent their time doing nothing but talking about and listening to the latest ideas.)" NIV translation
So, they took Paul to the Aeropagus which would have been something like a city council. The people in the city were always wanting to hear and discuss the latest trends in beliefs. They were simply going to give these "strange ideas" consideration. Doesn't it seem like the same thing happens in our society today? Instead of accepting God's Word, many people are looking for the latest and greatest trend, even in their faith.
"Paul then stood up in the meeting of the Aeropagus and said: 'Men of Athens! I see that in every way you are very religious. For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD. Now what you worship as something unknown I am going to proclaim to you." NIV translation
We have heard the expression "covering all bases". Well, that is exactly what the people of Athens did in worship. Paul described them as very religious, even to the point of building an altar to a god they couldn't even name. You see the same thing is happening in the world today as many people are very "religious" but they don't know the Lord Jesus. Jesus made it perfectly clear that He is the ONLY WAY to forgiveness and having a right relationship with the Creator of the universe. Today, more and more people want to compromise and even blend elements of different faiths to "cover all bases" but there is only One Way and One God.