John Frame notes that the Greek word behind "sound doctrine" in 1 Tim 4:6 ("good doctrine" in the NKJ) is hygiainos, where we get our word "hygiene." Doctrine is to be "health-giving" to the soul of man. In fact, it is to be life-giving to the whole man. (see Frame, Systematic Theology, p7).
Theology is to be taught not only to give us truth about God. It is to make us more like God. It is to build us up into the new humanity that we are in in Christ.