Inerrancy means that the Bible does not contain errors or contradictions. This applies only to the original autographs. Put simply, when God moved authors to write, they wrote what God willed them to write, and since the Lord is perfect and cannot ere, what was written originally was without error. The word of God is always true. The Bible is never false in anything it affirms, whether it be doctrine, ethics, or science (such as social, physical, or life science).
Inerrancy extends only to the original manuscripts. Copies and copies of copies may contain errors because they were copied by fallible humans who make mistakes. These errors or inaccuracies are always minor. They are usually copying errors and do not change or affect doctrine or anything of importance. Other errors may be in translations. Words or phrases may be interpreted or translated incorrectly (the Latin Vulgate is an example of this).
However, God in his providence has overseen thousands of copies and their transmission. What we have today, since the originals have been lost to time, is what God desires his church and children to possess. When manuscripts are compared to older manuscripts (which have less copyist errors because they are older and have been copied from copies closer to the original source), errors can be detected and corrected. It is believed that the copies of Scripture we possess today are 99% accurate in comparison to the originals. The more copies that are compared, the more errors are discovered. The more errors that are discovered, the more errors that can be fixed in order to get that much closer to the original manuscript.
The Bible itself argues for inerrancy. In fact, inspiration requires inerrancy (2Tim. 3:16). If the word of God is breathed out by God, then it follows that since God is indeed perfect, his word is without mistakes or errors. Divine messages are absolutely true and trustworthy. But, what is false fails. God explained this through Moses in Deuteronomy.
“If a prophet or a dreamer of dreams arises among you and gives you a sign or a wonder, and the sign or wonder that he tells you comes to pass, and if he says, 'Let us go after other gods,' which you have not known, 'and let us serve them,' you shall not listen to the words of that prophet or that dreamer of dreams. For the LORD your God is testing you, to know whether you love the LORD your God with all your heart and with all your soul. You shall walk after the LORD your God and fear him and keep his commandments and obey his voice, and you shall serve him and hold fast to him. But that prophet or that dreamer of dreams shall be put to death, because he has taught rebellion against the LORD your God, who brought you out of the land of Egypt and redeemed you out of the house of slavery, to make you leave the way in which the LORD your God commanded you to walk. So you shall purge the evil from your midst.” (Deut. 13:1-5)
“But the prophet who presumes to speak a word in my name that I have not commanded him to speak, or who speaks in the name of other gods, that same prophet shall die.' And if you say in your heart, 'How may we know the word that the LORD has not spoken?'- when a prophet speaks in the name of the LORD, if the word does not come to pass or come true, that is a word that the LORD has not spoken; the prophet has spoken it presumptuously. You need not be afraid of him.” (Deut. 18:20-22)
If what was said happened, it was from God. If the words failed, the prophet was false. The main thing to see is that God gave his people a way to test the message and messengers. This would not be possible if the words of God contained errors. Since they were given criteria to distinguish the true from the false, it follows that God's word is always true.
The Bible is also authoritative which requires inerrancy. Matthew 5:17-20 and John 10:34-35 demonstrate that the law's authority hinges on the fact that it must be fulfilled. “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished. Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven.” (Matt. 5:17-20)
“Jesus answered them, 'Is it not written in your Law, 'I said, you are gods'? If he called them gods to whom the word of God came-and Scripture cannot be broken...'” (Jn. 10:34-35)
Scripture cannot be broken and is, therefore, binding and authoritative. In order for something to be absolutely authoritative it cannot contain errors. The trustworthiness and inerrancy of Scripture derives from the character of God. God cannot lie, make mistakes, or communicate errors (Num. 23:19; 1Sam. 15:29; Tit. 1:2; Heb. 6:18). He is perfect.
What cements the inerrancy of the word of God is 2 Timothy 3:16-17. “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be competent, equipped for every good work.” As was already discussed, the Scripture is exhaled or breathed out by a perfect God. He has given the church his word in order to equip her for good works that result in God being glorified. Also, the word of God is central to the life of the church. God's words are profitable. They teach, reprove, correct, and train. This would be impossible, however, if the word of God contained errors.
Remember, God gave his church his word. It is to grow and glorify God by following his word. How would this be possible if his word contained errors? If it misled? If it taught something that was wrong? If it could not be trusted? The word of God is inspired, and as a result, the word of God is inerrant. Scripture can be trusted because our great God is trustworthy and able to communicate truthfully and accurately his will to his church.