Part I
Part II
Part III
The Way of the Master claims to bypass reason and aim at the conscience:
You don't need to be an espert in apologetics. Instead, you'll learn the forgotten biblical principle of bypassing the intellect (the way of argument) and speaking diretly to the conscience (the place of knowledge of right and wrong) - the way Jesus did (Training Manual, blurb)
It is this unbelieving, anti-God, Law-hating carnal mind that we're trying to reason with in appealing to a sinner's intellect. We must therefore, as soon as possible, find a place of harmony between the sinner's mind and God's Law. (Training Manual p. 73)
There is something in this. There are intellection questions that are raised simply to avoid having to take God seriously. There are doubts which arise out of personal sinfulness. We do suppress the truth by our wickedness.
And yet I think the WOTM approach is both too optimistic and too pessmimistic about human nature.
1. Too Optmisitic
About the conscience. The Fall affected our whole nature, not simply our intellects. Our consciences also can be darkened, seared, hardened, distorted. See, for example, Philippians 3, 1Timothy 4 or Titus 1. In fact, much of the prophetic rebuke of the Jewish nation is that they were at peace in their religious hypocrisy.
Thoughts and sin mututally influence one another. On the one hand, as WOTM says, our sinful behaviour can distort our thinking. But on the other hand, our sinful ideas can produce sinful behaviour, which is technically consistent with our thoughts.
Therefore, certain non-Christian behaviours are, from the conscious and subjective point of view, full of integrity because they are in line with their intellectual worldview. It is the worldview itself that is the primarily sinful thing!
There is a place for discussion the intellectual arguments against the existence of God, and so exposing the sinful ideas; just as there is a plce for discussion of our moral failure and so exposing sinful consciences. Both are needed.
2. Too Pessimistic
Both conscience and intellect can be appealed to, to some extent. Although both are fallen, both still do function. in fact, there are some places in the Scriptures where human reason and motivations are spoken of surprisingly positively - for example Romans 7 (if taken to be speaking about a non-Christian, as I do), or Romans 10:1-3 or the Thessalonian 'nobility' in Acts 17.
While teaching that the human mind is objectively darkened by sin, the Bible can still speak of legitimate subjective motives.