A term is “clear” when its meaning is clear and you use it consistently according to that meaning in an argument. However, when a term is ambiguous or used in two different ways (i.e., equivocally), it introduces a fallacy, either because of ambiguity in meaning or because of grammatical ambiguity.
An example of ambiguity in meaning is the word “cut,” which has a variety of meanings: a share in the profits, a wound made by a sharp object, being dropped from the team, a slice of meat, a cost reduction, a style of clothing fashion, a command to stop (i.e., “Cut it out!”), and so on. The phrase, “He made the cut,” could refer to an athlete who is selected for a team, or a surgeon who makes an incision, or an office manager who eliminates an expense.
Or consider this recent Wall Street Journal headline that provides another example of ambiguity:
“GOP Lawmakers Grill IRS Chief over Lost Emails.”12
As someone pointed out, “This type of sentence has great possibilities because of its two different interpretations: (1) Republicans harshly question the chief about the emails; and (2) Republicans cook the chief using email as the fuel.”13
Grammatical or syntactical ambiguity occurs when the structure of a sentence renders its meaning unclear, often because of word order or because of incorrect or missing punctuation, such as: “The typical American eats more than three Greeks”; or “The police caught the man with a net.” Or compare: “Please don’t stop” with “Please don’t! Stop!”
It’s crucial to use clear, unambiguous terms when engaging in apologetics. Here’s an example: the term “world” is used here, clearly and consistently:
Jesus said, “For God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life.” (John 3:16, emphasis added)
In the context of this passage “whoever” is universal and literal, it means everyone. Thus, you and every other human being are part of the world to which Jesus is referring. Therefore, because God so loves you, he gave his only Son so that you should believe in him and therefore not perish but have eternal life.
To contrast, “world” in the phrase “Athanasius against the world” (Athanasius contra mundum)14 is neither universal nor literal. The great fourth-century Church Father was not literally opposed by everyone in the world in his defense of the divinity of Christ, though he was by many.
Arguments: “A group of statements, one or more of which (the premises) are claimed to provide support for, or reasons to believe, one of the others (the conclusions). All arguments may be placed in one of two basic groups: those in which the premises really do support the conclusion and those in which they do not, even though they are claimed to. The former are said to be good arguments (at least to that extent), and the latter bad arguments.”15
Example of a good argument: When Jesus declared, “Before Abraham was, I am,” the Jews “took up stones to throw at him” (John 8:59). And when Jesus said, “I and the Father are one,” the “Jews took up stones again to stone him,” and said, “We stone you for no good work but for blasphemy; because you, being a man, make yourself God” (John 10:30–31). Therefore, the Jews clearly understood that Jesus claimed to be God.
(The first two premises are demonstrably factual, as evidenced by the Lord’s countless miracles, knowledge of the secrets of the heart, etc., described in the New Testament, and the conclusion — that Jesus is God — logically follows from those premises.)
Example of a bad argument: Religion entails the worship of God. Most violence in the world is caused by religion. Violence, however, is incompatible with the concept of a benign “God is love” divinity. Therefore, religious violence is evidence that God does not exist.
(The first premise is true, but the second is false, the third is ambiguous [i.e., “violence” is open to multiple meanings, such as man-caused physical violence, the violence of nature and the elements, etc.], and the conclusion does not logically follow from the premises.)
Kreeft explains these elements thus: “A term answers the question what it is. A proposition answers the question whether it is. And an argument answers the question why it is.”
Statement/Proposition: “A sentence that is either true or false … typically a declarative sentence or a sentence component that could stand as a declarative statement.”16 The essence of apologetics is evaluating, critiquing, and demonstrating either the truth or falsity of statements/propositions made about God and His revelation to the world, as well as about everything that pertains to those “meta subjects,” including the Bible, Apostolic Tradition, the Church, the sacraments, et cetera. For example,
• God exists.
• Mary did not have other children besides Jesus.
• The sacrament of Baptism regenerates the soul of the one baptized.
• The Bible does not teach the principle of sola scriptura.
Kreeft adds a further precision: “A proposition has two structural parts: the subject term and the predicate term. The subject term is what you are talking about. The predicate term is what you say about the subject. The word “subject” and “predicate” mean the same thing in logic as in grammar.17
Premises and Conclusions: “The statements that set forth the reasons or evidence, and … the statement that the evidence is claimed to support or imply…. [T]he conclusion is the statement that is claimed to follow from the premises.”18 In any argument, one or more of the premises must make a claim that it seeks to prove or infer explicitly in the conclusion, which is indicated with words such as “therefore” and “thus.”
Premise: Jesus Christ, who is God incarnate, promised that the gates of hell will not prevail against the Church.
Premise: God cannot lie.
Conclusion: Therefore, the Church Christ established will never totally apostatize.
A claim can also be logically inferred implicitly through premises, for example, in this way:
The earliest Christians clearly understood what Jesus meant by saying, “This is my Body” and “This is my Blood” at the Last Supper.
The Apostles explained to the earliest Christians all that Jesus said and did and what he meant by what he said and did.
The Apostles knew what Jesus meant by what he said and did because they were eyewitnesses to this event and because Jesus explained everything to them (see Matthew 13:36, 16:5–12, Mark 4:34).
The next component is validity. For an argument to be sound, it must have clear terms, true premises (i.e. claims), and valid logic, in which case the conclusion will necessarily follow. Here are two examples of valid arguments, beginning with a classic formula:
All men are mortal.
Socrates is a man.
Therefore Socrates is mortal.
All two-dimensional shapes that have three sides are triangles.
This two-dimensional
