Sermon: Do You Make Men Thirsty?
Scripture: Matthew 5:13
In this week’s lessons, we learn what it means for a Christian to live for Christ in the world.
Theme: From Abstract to Function
At verse thirteen of the fifth chapter of Matthew’s Gospel we come to a new section of the Sermon on the Mount. We pass from a basically abstract definition of the Christian to a functional one. Jesus said, “Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? It is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.”
We all know the difference between an abstract definition of a thing and a functional definition, if we think about it. For instance, almost every dictionary definition of a word is abstract. We turn to the word “hunger” in Webster’s New Collegiate Dictionary and read, “an uneasy sensation, occasioned normally by the want of food.” However, we could also define hunger functionally. We could say, “Hunger is the one and a half billion people in this world who live always on the verge of starvation and who die at the rate of 100,000 daily as the result of malnutrition.” The second definition is anything but abstract. And, of course, it is better. In the same way, the dictionary tells us that “justice” is “the principle of rectitude and just dealings of men with each other.” But we could also say that justice is enacting good laws, caring for the poor, raising children properly, and many other things.
We have the same thing in the sphere of theology. The Westminster Shorter Catechism asks the question, “What is God?” Then it answers, “God is a spirit, infinite, eternal, and unchangeable, in his being, wisdom, power, holiness, justice, goodness, and truth.” But it is also true, even more true, that God is Jesus Christ who died for our sin and who rose again for our justification. 
The second definition in each of the cases I have mentioned carries listeners away from any detached or abstract understanding of the term to an understanding of the term in action, and it produces the effect that Jesus also produced in his listeners by his further, functional definition of the true Christian. “Ye are the salt of the earth.” “Ye are the light of the world.” By these definitions Jesus was saying that while it is true that the Christian is to be poor in spirit, mournful for sin, meek, thirsty for righteousness, merciful, pure in heart, and disposed to make peace, nevertheless he is never to be these things in isolation from a very real and sharply antithetical world. He is to manifest those characteristics in the world. What is more, he is to practice these things in a way that will affect the world positively, as salt affects the medium to which one applies it. 
Study Questions:

What is the difference between an abstract definition of something and a functional one?
How do these two definitions apply to the Sermon on the Mount up to this point?

Prayer: As you study this week, ask the Lord to give you understanding of how you can be more effective salt as a Christian in a wicked and hostile world.

Study Questions
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