Intelligence by Faith - Romans 12:6

Let us prophesy according to the proportion of faith.

Here, Paul is teaching about spiritual gifts. Saying if yours is the gift of prophesy, then use it as much as the faith given to you will permit. Faith is a gift of ability and courage to listen to and follow the Spirit. The spirit of truth is also known as the Light of Christ. It permeates all things and infuses them with truth. However, we must be listening on the correct wavelength. Even if we've tuned into the right frequency, we don't necessarily have what is necessary to convert that light and truth into something that we can understand.

Remember that the glory of God is intelligence, or, in other words,light and truth; and truth is things as they really are, and of things as they really will be. (Jacob 4:13) Thus by faith, the spirit of prophesy is the reception of truth about things which are to come - and the spirit of discernment is the reception of truth about things as they are. These gifts are only as useful as our ability to tune to truth and light, and convert it to something intelligible. That is where the Holy Ghost comes in - it helps us to "feel" the truth and understand it.