Ear Training and Sight Singing

>From "Essays on Violin Pedagogy" by Lyman Bodman, under "Ear Training and
Sight Singing":

"No one, but no one, who cannot hear melodic intervals can play a violin in
tune."

First of all, what does this mean?  That you have to be able to say "that's
a perfect fifth or perfect third" or whatever?   The rest of this short
essay goes into singing the notes before playing them.

Second, do you agree or disagree?  I am too much of a beginner to be able to
comment myself, but a lot of you are quite advanced.

Third, any suggestions for good solfege self-study courses out there?  How
about the David Lucas Burge Relative Pitch course (available over the net)?

Since I am off the fiddle for a bit (injury), this might be a good time to
get into this sort of activity.

Astrid.