We speak by letting air flow from our lungs and through our vocal cords, located deep in our throats.
The Phoenician abjad was all consonants. A consonant is a hard sound you make in your mouth by closing off the air flow from your lungs. You make ‘D’ or ‘T’ by pressing your tongue to the roof of your mouth then releasing air. You make ‘K’ by closing the back of your mouth, then releasing air. Close your lips then pop ‘em open to make ‘P.’ Every consonant is made by closing the air flow in your mouth, then releasing it. To make ‘H, R, W & Y’ you don’t cut off air flow completely, but you do restrict it by a lot. You push a sudden gust of air out to say ‘hey.’ You lips and mouth tighten up to say ‘roo woo yay.’
On the other hand, vowel sounds are made by keeping your mouth open and letting the air flow freely. You adjust the shape of your open mouth to make ‘A, E, I, O & U.’
‘Y’ can be a vowel or a consonant.
Homer needed vowels to compose and recite poetry because a vowel can be extended over more than one beat. Try singing this without vowels: https://www.youtube.com/watch?v=ZbrnXl2gO_k
Back to the beginning of The Western Civ User’s Guide to Reading & Writing.