Mightest know (epignwi). Second aorist active subjunctive of epiginwskw. Full knowledge (epi-), in addition to what he already has. The certainty (thn aspaleian). Make no slip (spallw, to totter or fall, and a privative). Luke promises a reliable narrative. "Theophilus shall know that the faith which he has embraced has an impregnable historical foundation" (Plummer). The things (logwn). Literally "words," the details of the words in the instruction. Wast instructed (kathchqh). First aorist passive indicative. Not in O.T. and rare in ancient Greek. Occurs in the papyri. The word hcew is our word echo (cf. 1 Thessalonians 1:8 for exhchtai, has sounded forth). Kathcew is to sound down, to din, to instruct, to give oral instruction. Cf. 1 Corinthians 14:9 ; Acts 21:21Acts 21:24 ; Acts 18:25 ; Galatians 6:6 . Those men doing the teaching were called catechists and those receiving it were called catechumens. Whether Theophilus was still a catechumen is not known. This Preface by Luke is in splendid literary Koin and is not surpassed by those in any Greek writer (Herodotus, Thucydides, Polybius). It is entirely possible that Luke was familiar with this habit of Greek historians to write prefaces since he was a man of culture.