Jude 3 “Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort [you] that ye should earnestly contend for the faith which was once [for all] delivered unto the saints.”
The Greek word translated "once" is "hapax" ἅπαξ. means "once for all." The Faith as given in scripture was delivered once for all and we are exhorted to earnestly contend for it against the myriad of new "winds of doctrine" spoken of in Ephesians 4:14. "Contend" means to struggle in rivalry, battle, etc.; vie, to argue earnestly; debate, to assert or maintain.
In Titus 1:9, Paul states that a qualification of a Bishop or Deacon is “Holding fast the faithful word as he hath been taught, that he may be able by sound doctrine both to exhort and to convince the gainsayers.”
And in 2 Timothy 4:2, Paul exhorts Timothy to “Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all longsuffering and doctrine. For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away [their] ears from the truth, and shall be turned unto fables.”
Contending for the Faith, for the truth of the Word of God is a requirement, not an option, for ALL believers. Although there is a specific gift of the Spirit called "Discerning of Spirits," the discernment ALL believers are required and commanded to use to contend for the Faith or the truth involves analytical thinking (logic, facts, and downright common sense).
Hebrews 5:14 states: “But strong meat belongeth to them that are of full age, [even] those who by reason of use have their senses exercised to discern both good and evil.”
reason of use: διά ἕξις dia hexus "through use"--a habit whether of body or mind; a power acquired by custom, practice, use
senses: αἰσθητήριον aisthētērion faculty of the mind for perceiving, understanding, judging
exercised: γυμνάζω gymnazō to exercise vigorously, in any way, either the body or the mind
discern: διάκρισις diakrisis a distinguishing, discerning, judging
good: καλός kalos beautiful, handsome, excellent, eminent, choice, surpassing, precious, useful, suitable, commendable, admirable
bad: κακός kakos of a bad nature, not such as it ought to be
But strong meat belongs to those who are mature, who through practice have vigorously exercised their faculty of mind for perceiving, understanding and judging to distinguish or discern both good and bad.
Another verse that emphasizes the use of our mind is 1 Thessalonians 5:21 “Prove all things; hold fast that which is good.”
The unassuming five letter word "prove" is easy to pass right over without really thinking about what it means. The Greek word translated "Prove" δοκιμάζω dokimazō means to test, examine, prove, scrutinize (to see whether a thing is genuine or not), as metals; to recognize as genuine after examination, to approve, deem worthy.
Scripture makes it clear that we are to know what we believe and why we believe it, and then to contend for the Faith using logic and reasoning coupled with wisdom and gentleness. The name for the method of contending for "The Faith" is Polemics which is frequently confused with Apologetics. Although it uses an Apologetic approach, it has different criteria than what is considered Classical Apologetics.
See: What is Apologetics?
See: What is Apologetics?
