I had a discussion with my oldest son about Plato’s Republic, and in particular the nature of justice. Out of many things said, it stood out to me that philosophers begin by assuming that we must debate over the meanings of things. I think that on the contrary, from the time we are two years old, and possibly younger, we know things about justice and love and truth and sin inherently. We can talk about justice knowing that all of us have a powerful and innate sense of what we are talking about. The theist speaks from the position that we are created in the image of God and that we have inherent true knowledge that we all share. C.S. Lewis points this out in Mere Christianity: if you listen to people argue, they try to win by appealing to a higher principle which they both adhere to. The naturalist does not have this assumption, and so we must first define terms carefully, such as justice, before we can speak. We cannot assume similar innate understanding of things, because that implies something perhaps spiritual or supernatural. I think the evidence is to the theist: we do have inherent knowledge, and it is difficult to explain as the result of evolutionary advantage. This is why the role of the philosopher is as a teacher or debater, while the role of the Christian is as a preacher. The preacher addresses that which people know but have trouble living in the light of that knowledge.
In 1 John 2:21 it says, “I have not written to you because you do not know the truth, but because you know it”. This is eido knowledge, similar to being a witness to a crime, as opposed to studying to become knowledgable about the law. We all have first hand ready knowledge of justice and love, and if we are believers, of Christ. We can talk about it and teach it, but we do not talk and teach and preach as if there is no common experience of these things, but as if there is common knowledge.