Heidegger's Bible Handbook: Harmony of the Gospels: Finding Historical Order in the Gospels
10. How might the histories of the individual years or Passovers be reduced to a certain series? It is demonstrated that in this matter the Evangelists stretch out their hands to each other.
For constructing a Harmony of this Gospels, this also is pertinent, that the history of the individual years, or of the individual Passovers, be not mixed together is some haphazard confusion, but that, as far as it is able to be done, it be investigated what might be the reckoning of the ἀκολουθίας/succession, in which course or order of progression, according to the series of the times and matters conducted, the histories appear to succeed one another; or, as Augustine says, which histories by probable reasoning are to be placed before which and after which. Therefore, the accounts of the order of sequence, if not everywhere certain, and always manifest (for our faith does not depend upon a precise account of times), are able to be rendered probable, and not absurd, or completely dissimilar. Indeed, of old Tatian thought that the narrations of the rest were to be accommodated to the context preserved by Matthew as the first. Others thought Mark to be the leader of this order; yet others, Luke, since he professes in his preface that he is going to write καθεξῆς, precisely and in order. Moreover, that the individual Evangelists kept the order of time accurate, Osiander was the first to persist in saying. But the matter itself shows that the Evangelists compared their works one to another, both in the matters that they narrate, and in the very order. Some histories are described with notes added, clearly arguing the sequence of time: others, without notes of this sort. Where Matthew omitted the notation, there the others posit the circumstances, from which an account of the order is able to be gathered. Where Matthew adds the notation, there the others omit the same, or make use of a transposition. Many things are also spoken by anticipation or ἀνακεφαλαίωσιν/recapitulation. A more precise order, although not accurate in all places, Mark and Luke preserve: and with respect to order Luke agrees with Mark in many things: but in certain things he neglects order in such a way that he ought to be supplied out of Matthew and Mark. He does not observe καθεξῆς/precisely the exact order of sequence, but either the accuracy of the matter, which he resolves to repeat and to describe thoroughly, and the uppermost heads of which to touch upon accurately: or that manner, in which something is described item-by-item, not παχυμερῶς/roughly and ὡς ἐν τύπῳ, as in a draft: or even the order of writing, because he wrote thereafter, or after the others. Therefore, others, both of the ancients, Theophilus, Epiphanius, Augustine, and others down to Gerson; and of the more recent generally; have tightly bound the order of the harmony to the context of no single Evangelist: out of a diligent συμβιβάσει/reconciliation, collation, and consideration of the circumstance that are found in the individual Evangelists; and out of the whole body of the Gospel history, they search out and gather the order of sequence, with certain general rules or observations employed to help.
 Luke 1:3: “It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order (καθεξῆς), most excellent Theophilus…”