2Pe 1:8-9, 8 For if these things are yours and abound, you will be neither barren nor unfruitful in the knowledge of our Lord Jesus Christ. 9 For he who lacks these things is shortsighted, even to blindness, and has forgotten that he was cleansed from his old sins.
In order to be efficient in the faith, we cannot be deficient in virtue, knowledge, self-control, perseverance, godliness, kindness, love, otherwise we become barren, unfruitful (2Pe 1:8), and shortsighted (2Pe 1:9). These qualities are the means by which you abound in fruitfulness, showing that you have the knowledge of Christ in reality.
He who lacks these is also shortsighted (unable to see things clearly, unless they are very close). He is unable to see beyond faults, failures, sins. In other words, he cannot see God working because he has lost evidence of things not seen. Heb 11:8 “By faith Abraham …10…waited for the city which has foundations, whose builder and maker is God.” He lived in a tent, yet he saw and envisioned a city by God from a distance and embraced it by faith. It served as a reminder that God who called him from a pagan country and gave him promises would be faithful to accomplish what He began. By faith he was fruitful even in his old age.
The full knowledge of Christ is the goal towards which all these graces tend. Where grace abounds, good works will increase. Abiding in Christ (John 15) is the means by which we bear fruit, more fruit and much fruit.