Mat 22:45 If David then call him Lord, how is he his son?
if certainly David named him master, how a son of his is he?
Interesting and Hidden Aspects:
This verse plays of the special meaning of the word translated as "lord" when it is applied to the head of a family. Note that Christ doesn't answer his own question nor does anyone ask him to. Instead, Christ simply makes it clear that on this central question of authority, the traditional Jewish viewpoints about the Christ and his authority were insufficient because the Christ did not get his authority from David, but the other way around.
The "if" here expresses a condition but it means nothing regarding whether that condition is met or not. Here, however, the condition was certainly met, but this is indicated by the following word.
The Greek word translated as "therefore" either emphasizes the truth of something ("certainly", "really") or it simply continues an existing narrative. Here, it is used in both sense, both to make it clear that David was certainly giving a clear title to the Christ and as to lead to a clear conclusion, even though that conclusion is a question.
The term translated as "called" is like our word "call" means both "to summon" and also "to name." Chriat has used this word consistently in the verses leadning up to this statement. The sense is clearly that David "named" that Christ his master.
The Greek word translated as "lord," means "having power", "being in authority" and "being in posession of." It also means "lord", "master of the house," and "head of the family." You can see the problem here more clearly if we focus n the "head of the family" meaning. This was its meaning when applied to a member of your family.
The verb "is" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition.
The word translated as "son" more generally means "child." It refers to all offspring in later generations, just like "father" refers to all previous generations. Christ also used it metaphorically to describe those that follow a way of thought or set of beliefs that descend from an individual. More about it in this article.
εἰ "If" is from ei, which is the particle used to express conditions "if" (implying nothing about its fulfillment) or indirect questions, "whether." It also means "if ever", "in case," and "whenever." It is combined with various conjunctions to create derivative conditions.
αὐτὸν (adj sg masc acc) "Him" is from autos, which means "the same," and the reflexive pronouns, "myself", "yourself", "himself", "herself", "itself," or the oblique case of the pronouns, "him", "her," and "it." It also means "one's true self," that is, "the soul" as opposed to the body and "of one's own accord."
κύριον, (noun sg masc acc) "Lord" is from kyrios (kurios), which means "having power", "being in authority" and "being in possession of." It also means "lord", "master of the house," and "head of the family."
αὐτοῦ (adj sg masc gen) is from autos, which means "the same," and the reflexive pronouns, "myself", "yourself", "himself", "herself", "itself," or the oblique case of the pronouns, "him", "her," and "it." It also means "one's true self," that is, "the soul" as opposed to the body and "of one's own accord." -- The word translated as "him" is the Greek word commonly translated as pronouns in English, but it has a few shades of meaning our pronouns do not have. The word technically means "the same," and when used as a pronoun can mean "the true self" as opposed to appearances.
The phrase plays of the meaning of "lord" as the head of the household when applied to a family member. That word is contrasted with "son," who cannot be the head of the household while his father lives.
Possible Symbolic Meaning:
In the end, this chapter comes to one conclusion: that all authority comes from God. Intermediary authorities, such as earthly kings, must be respected, but only within their own realms. There is a strong hint here that the realm of the Messiah reaches beyond this world to the next. The only other place in the Gospels that Christ mentions a "footstool" is when he referred to the earth as God's foodstool.