The plural of the imperative: “believe ye me.†Compare believest thou, Joh 14:10. These words are addressed to the disciples collectively, whose thought Philip had voiced.
Or else (εἰ δὲ μὴ)
Literally, but if not. If you do not believe on the authority of my personal statement.
For the very works' sake (διὰ τὰ ἐÌÏγα αὐτὰ)
Literally, on account of the works themselves, irrespective of my oral testimony.