The vowels:

A, E, I, O, U, and sometimes Y and sometimes W.

So words can be made entirely of vowels: way, woe, you, yaw, wye, iou and others. Aye and awe are another two.

But if you add vowels that "didn't make the cut" like the Thorn and the Ampersand the list increases.

Of course, Amos is speaking only of Roman-based alphabets (who stole them from the peoples of the far end of the Mediterranean, like the Phonecians (who spelled everything Phonetically). ㄱ(or "g") is the first letter in Hanguel, the Korean alphabet. This would may gnu the first.

Amos, your world view is too parochial.