The Lord Jesus said in the Sermon on the Mount in Matthew 6:24:

No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other.

Related to this is something the Apostle Paul wrote in 1 Corinthians 7:22-23:

For he that is called in the Lord, being a servant, is the Lord’s freeman: likewise also he that is called, being free, is Christ’s servant.  Ye are bought with a price; be not ye the servants of men.

Furthermore from Paul comes Romans 6:16:

Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?

From these three passages or verses we get some basic, simple truths for all of life.

To put everything above together, every person has one master or lord, just one, and he is a slave to one or the other.  He cannot love them both.  He loves only one of the two and then hates the other.  If the master is Christ, then He is owner, based on the reality that he bought the person.  The slave obeys His master, whichever one it is.  Obedience will occur one way or the other.  This obedience to the master is yielding to the particular master, whichever one.

A person chooses his master or lord.  If he chooses Jesus as his Lord, this is faith.  He believes in Jesus.  The belief is a belief in reward or goodness (Rom 2:4; Heb 11:6).  If someone doesn’t think he will be better off, he will not choose that master.  For Jesus, it is a matter of faith, based on evidence (Heb 11:1-3).  God’s Word is true, so someone can trust what it says about his present and future.  He turns from the other direction, what would be an idol, to Jesus Christ.

Satan and the world system interacts with someone’s flesh to persuade him to take a different master than Jesus Christ.  The world offers someone things that seem like a lot to a person, feigning competition with God.  Paul calls it dung, whether it be possessions, positions, passions, or popularity (Philip 3:8).  The trade is nothing for everything, which is why Jesus said (Mark 8:36):

For what shall it profit a man, if he shall gain the whole world, and lose his own soul?

A person loses everything the world offers.  It is short term only.  Even then it doesn’t satisfy, which is why Solomon said it was all vanity.  It is about volume.  More and more.  Enough is never enough.

The choice is stark and plain.  You go one way or the other.  There is no middle ground.  That is reality.

A different picture is depicted than reality.  The false portrayal, that the god of this world and his world system present, is that both sides can be straddled.  You really don’t have to choose.  Many, if not most, churches participate.  People want the world, because of the short term benefits it offers, and because they don’t want what Jesus might offer in and for the short term, so churches turn the world into a church, so they’ll want the church.  The problem, of course, is that it isn’t exactly the church anymore, but it is a way of straddling the two masters.

In the end, there is still one Master.  It is Jesus.  It’s all true all the way to the end, that Jesus is Master.  Those who reject Him do not get the other way.  The world doesn’t have anything to offer.

The problem with blending the two Masters is that it confuses the world and the church about the One, True Master.  It’s true that no man can serve two Masters.  The people fooled aren’t serving Jesus.  They just think they are.  They are even being told they are with explanations that they are and how they are.

The people that make their way through to the kingdom relinquish themselves to Jesus Christ.  They choose Him as Goodness.  Jesus is the Master, but they are saved because they believe He is.  That is Who He is and they are acknowledging it and acquiescing to Him.  They gain everything.  Those who don’t, lose everything.