Sense of ResNet

[gent.spah]

Question about residual blocks and skipped connections

I understand that the purpose of the residual block is to mitigate a vanishing gradient, with the output of the residual block: a[l+2] = g ( W[l+2] . a[l+1] + b[l+2] + a[l] ) Firstly, in the case that the gradient goes to zero, does this not only affect dW, db? So rather than W, b → 0 would they not instead just remain constant? Surely for W, b → 0, this would have to have been learned and therefore suggest optimality? Secondly, why do we need the skipped connection? If instead we had: a…