For this very reason, make every effort to supplement your faith with virtue, and virtue with knowledge, - 2 Peter 1:5 (ESV)
The second character quality Peter names is knowledge. This comes after virtue in the list of character qualities with which we are to supplement our faith.
Almost immediately, there is an apparent problem with knowledge. It is all too easy to focus so much on knowledge that the other qualities are minimized. It is similarly easy to focus so much on the other qualities that knowledge is minimized. I have been around people (and have been guilty myself) who seemed to treat knowledge as the end in itself. Knowing facts and learning was the goal, with nothing beyond. Conversely, I have been around people who seemed to treat knowledge as though it were a contaminating substance which corrupted love and kindness and should therefore be avoided. Their argument was that knowledge is an obstacle to love; the less people thought, the more they could love.
Knowledge can be a polarizing issue among Christians. Why is this so? Three words: knowledge puffs up (1 Cor. 8:1). Ever since the fall of man in the Garden of Eden, human nature has been bent. We are inclined to exalt ourselves over against God rather than humble ourselves before him (e.g., the Tower of Babel - Gen. 11). We are constant comparers, comparing ourselves to God, to others, and to past and future versions of ourselves. A little knowledge, real or not, is perhaps the fastest way to inflate our own view of ourselves. Knowledge makes us feel better about ourselves. It puffs us up.
On the other hand, others of us seem almost intuitively to grasp the way others distort knowledge from its intended end to serve pride. And so we ignore it, choosing to emphasize instead less easily distorted qualities such as kindness, hospitality, and generosity to start. But in doing this, we make a converse error to the one we try to avoid. In pursuing kindness, hospitality, and the like without knowledge, or with a depreciation of it, we can make our kindness mindless.
What is knowledge? It is information, but it is more than that. Knowledge is an apprehension of facts. It is familiarity with ideas. To have knowledge is to have an understanding of information. It is common to point out that knowledge is not purely intellectual. It is relational as well. To have knowledge is not only to be aware of information but to have a connection to its subject.
We make a distinction between knowing and knowing about. To know something is to have a certain sort of intimacy with its object. To know about something is something less, it is to have some facts that may be true, but without strong familiarity. I may know about a language, but that is not the same as knowing the language. I may know about a person, but that is not the same as knowing the person.
How do we understand knowledge as Peter uses it? We should understand knowledge as that of relationships as well as facts. Scripture speaks about knowing God in other places, using the same word that Peter does here. Paul speaks of knowing Christ (Phil. 3:8). Paul also writes about spreading the knowledge of Christ (2 Cor. 2:14) and compares our knowledge of God to light that God causes to shine (2 Cor. 4:6).
But other examples make clear that knowledge is not restricted to knowing God in relationship. Knowledge is something you can have about the nature of food sacrificed to an idol (1 Cor. 8:7). All the treasures of knowledge are hidden in Christ (Col. 2:3), and invalid arguments are called false knowledge (1 Tim. 6:20).
Why does knowledge come after virtue? There may be no special significance to this fact. On the one hand, you cannot pursue virtue without an understanding of what constitutes virtue, which implies knowledge. On the other hand, if our hearts are not inclined toward virtue, then the only effect we can expect from knowledge is to be puffed up.
Why is knowledge so important? There are many potential reasons, but one stands out to me: you cannot love God better than you know him. Is this axiomatic? I take it to be so. And yet so many of us are content with our ignorant misconceptions of God that we fail to recognize the God we seek to serve is a god more of our own making than the God who reveals Himself in creation, in the Bible, and through Jesus Christ.
A. W. Pink said, “Christ cannot be trusted at all unless he be known, and the better he is known the more will he be trusted.” (Profiting from the Word, page 40). Knowledge supplements your faith because the strength of your faith is limited in proportion to the extent of your knowledge of its object. Knowledge is to faith what wood is to fire; if the wood is kept separate, it does nothing for you, but if you place the dry wood in the fire, it will burn all the brighter, hotter, and longer. If you do not gather wood, do not be surprised at having a small and weak fire.
Knowledge supplements faith by removing ignorance and clarifying the connections between what you depend on/trust in and everything else in life; knowledge supplements your faith by keeping your focus on what is real and true and not on passing doctrinal fads; knowledge helps preserve your faith in the right things so that you grow strong in Christ and are not tossed to and fro and driven about by whatever superficial things the person leading may happen to be saying.
Knowledge in the abstract is neither evil nor an end in itself. Knowledge is an essential part of the Christian life. The purpose of Christianity, even life itself, can be summarized as knowing God. We cannot hope to live for God through Christ with empty heads. But neither will we live for God through Christ if we stop at the apprehension of mere facts. Our growth in knowledge must be intended to serve our relationship to God, not to undercut, subvert, or replace it. If we pursue knowledge in the abstract as a means of knowing God personally, we can be confident that God will bless it and make us fruitful.