Q1. (1 John 5:4-5) How does a defeatist mentality differ from a belief that in Christ we have overcome the world?
These two thoughts are diametrically opposed. The defeatist mentality comes out of the realization that the flesh cannot do anything by itself. When we try everything, including looking for our politicians, to save us from the world we find ourselves in this defeatist mentality. On the other hand, when we realize that Christ has done the work of overcoming, we rejoice in his victory.
What part does faith have in this overcoming?
Faith is in believeing what we cannot see, hence we do not "see" with our eyes in the victory. We nonetheless know we have victory because we read these truths from scripture.
What part does unbelief have in a defeatist mentality?
We are defeated when we lack the faith to believe in Christ.