Please read the passage before reading the commentary.
John writes to a Christian community, a Church, whom he calls, Chosen Lady. There are problems in the community. John is happy that some are walking in the truth, even though not all are in the truth.
There is not more than one absolute truth, even though we like to think that our share in the truth is the only totality of the truth. John gives us a sign for the truth: if we love one another, we are living in the truth.
There are, however, many deceivers in the world. They do not love, and they do not acknowledge that Jesus Christ has come in the flesh. If they do not have Jesus Christ as Son of God, they do not have the Father. Only a person who has a child can be known as a parent. If God has no Son, then God cannot be Father.
It is the love of God as Father for Jesus the Son that outpours into us who believe in Jesus. Love, then, becomes the basis of belief. The truth of God as Father and Son is revealed in their love of one another and for us. Our possession of the real truth is revealed in our love for one another because our love reveals God’s love.
Continue, then, to walk in the truth, loving one another as God has loved you.