Philosophy of Discipleship
Many Christians believe that the heart of the Great Commission is evangelism. In reality, the heart of the Great Commission is "making disciples" -- which is the main verb of Matthew 28:19-20. The focus is making disciples, but the ultimate goal is the worship of God. Evangelism is the first step, but then as one commentator noted, "Discipled implies a process of teaching and training beyond evangelizing" (Acts 14:21-22).
Discipleship begins a long (and often slow) process of teaching new converts the truths and doctrines of the Christian faith. Notice what is involved in this process (according to Matt. 28:20); "Teaching them to observe all things that I have commanded you." First, making disciples involves teaching. This is much more than a "new converts class" in Sunday school. Christ told us to teach them "all things" (or "all the counsel of God" as Paul put it; Acts 20:27). Seminary students spend years (full-time) studying the various doctrines and disciplines of the Word of God. So "making disciples" in the local church inherently means a long, slow process.
Second, true disciples will "observe" the commands of Christ. This involves "heeding" the commands internally and "practicing" them externally. This does not happen naturally -- especially for those who indulged their flesh before they were saved (Jeremiah 13:23). So "making disciples" also involves training in addition to teaching. Such "training" is described elsewhere in Scripture. I Timothy 4:7 says to "exercise [train] yourself toward godliness." Hebrews 12:11 describes the chastening of God as initially painful, but then "afterward it yields the peaceable fruit of righteousness to those who have been trained by it." Hebrews 5:13-14 speaks of spiritual infants as "unskilled" in using the word of righteousness, but those who are mature are the ones who "have their senses exercised [trained] to discern both good and evil." This refers to more than just a head knowledge of Christian doctrine.
Training is necessary for two reasons. The first reason is to increase strength. One of Paul's goals was to strengthen new converts (Acts 14:22) in preparation for the suffering that would come. The second reason is for discipline. Christians should discipline their minds to always react in a calm, gracious manner; or to always trust God in our circumstances; or to always pray for God's guidance in making a decision, etc. Discipline and strength are two important ways to train Christians and to produce mature disciples.
Finally, Scripture says the immature believer is like an infant consuming only milk, and the mature believer is like an adult who can eat meat or solid food (Heb. 5:12-14). The obvious implication here is that those who are mature (i.e. those who receive instruction and work at training themselves) can understand more -- deeper Biblical truths that are referred to as meat or solid food. The more Christians understand about God, the greater their worship of Him will be.