Here Lawrence introduces the "tools" of biblical theology and how to use them.
Lawrence gives an example of the different "horizons" of a person's life: the public, personal, and private horizons. Each is true about the person, but doesn't give the entire picture. As you view the person from each horizon, you learn something more about who he is.
Similarly, we view God's revelation of himself in different horizons: the textual, epochal, and canonical horizons.
The textual horizon, per Lawrence, is the closest view and consists of what the text actually contains: its language, verbiage, and terminology. The epochal horizon and canonical horizon seem to overlap somwehat in Lawrence's description.
Epochs are sometimes delineated by the presence of a new covenant -- or promise by God -- for instance. Epochs seem to be turning points at which at bit more of the revelatory curtain is pulled back to expose God's design and plan of redemption (called "progressive revelation" by some). Lawrence cites the division between the Old and New Testaments as an obvious epochal division.
Covenants are God's promise to men regarding future salvation and blessing. These are ultimately fulfilled in Christ.
Adressing a passage of Scripture this way would initially reveal the textual horizon -- what the text actually says -- then the reader would "back out" a bit and view the epochal horizon -- what stage of redemptive history the text was given -- then assess the covenantal horizon and how this particular text might have been fulfilled in the first coming of Jesus, or how it will be fulfilled in his second coming.
Lawrence uses as an example of this process a text that fits all three horizons, but there are some passages for which the "horizon" view might not work so easily, and Lawrence gives no guidance at this point regarding how to treat those passages.
Even so, Lawrence's description is useful, and helpful to emphasize the importance of viewing each passage of Scripture no only in isolation, but in connection with other teachings of Scripture; in considering, as it were, the stage of redemptive history in which the passage was given.
Lawrence's next chapter addresses prophecy and typology, among other things.