We want always to interpret the bible in such a way as to not violate the basic principle of Scripture's unity and integrity." R. C. Sproul
The "analogy of faith" means that Holy Scripture is its own interpreter. We interpret Scripture according to Scripture. Behind this principle is the belief that the Bible is the inspired Word of God. Since it is, it must be consistent and coherent.
Principles of Interpretation:
1. The "analogy of faith", a doctrine espoused by the Reformers, means that Scripture is its own interpreter. We interpret Scripture according to Scripture. We interpret the meaning of a verse in light of the overall teaching of the Bible. Since God is omniscient, he would not contradict himself.
2. We interpret the Bible literally ("sensus literalis"). We interpret passages in the sense in which they were written. For example, we interpret a parable as a parable, not as narrative. We do not interpret narrative as metaphor. We read the Bible as we read any book in this manner. God, through the Biblical writers, conveyed his messages in ways the original audience understood, and as we can understand. This means we do not impose secret meanings (Bible Code). But it also means we do not take symbolic passages as narrative in a "wooden literalism". We use ordinary rules of language to interpret the Bible.
3. We interpret the implicit by the explicit. That means we do not imply a meaning to a passage greater that what it actually says or in a manner that contradicts other passages. This is often done to "proof text" a point. For example, if this verse says "x", it implies "y"must be true. If other passages show "y" is not true, that cannot be a correct interpretation.
4. We interpret obscure passages by clear passages. We do not reverse that process. That is how heresies often start. We do not use an obscure passage to show the whole message of the remainder of the Bible is not true. We always interpret scripture in a way that preserves the integrity and unity of the whole.
Sources: various readings, including R.C. Sprout's "Knowing God" and "Knowing Scripture", TableTalk Magazine, Vo. 35, No. 1, January 2011, p. 4 et seq.