Astrology is the original language of inter-relatedness. In fact, it's a declaration of inter-dependence. The language says there is a harmony a correlated-ness that run throughout creation that we cannot pluck one stand without resonating the whole. I view astrology as a primary language of liberation, a tool for inner access, non essential. We don't need astrology but it's wonderful and exquisite, beautiful language that feeds our intuition.
Astrology is at lease three folds. One, its descriptive. Two, it's instructive. Three, its celebratory and devotional. (go back to Chap.1, 11:20 for more note)
Mercury is the mind and intellect, our vice, how we speak, what we speak about. It's more important than mere word "intellect." Because in any metaphysical system, how we think, what we think about, what we say especially is considered "magic." Mercury is "the magician." And we are invocative. Which is always so crucial to watch what we say. So Mercury is the power of voice to make language and magical and summon actual reality.
Venus is the goddess of beauty, and art and kinship, Venus in a chart describes that which we love, what we value, how we love, how we value things, how we relate in general, how we are social, how we are intimate.