Volume is often called the 'godly' indicator. Price can't move without it - hence volume leads price.
This is incorrect. Volume represents the number of shares et al traded. If nothing is traded, i.e., printed, then there is no volume for anyone to see, except perhaps for those trading the ladder who are aware of unrealized volume. Volume and price are therefore simultaneous. One does not and cannot precede the other unless one is operating according to some special definition of "volume". And while it may be true that "at bottoms it takes very large buying volume to push equity prices up out of congestion & start the markup stage", it is also true that large volume (all volume is both buying and selling volume or else there's no transaction and thus no print) can serve only to retard or halt a decline (or rally). That large volume can also precede an extended ranging period or even a continuation downward (I'm sure that 1a can find many examples of this). The quantity of volume does not and cannot predict direction in and of itself. The test of what appears to be a low is much more informative. If price appears in real-time to make a higher low and the prints are accompanied by less volume, this suggests that selling interest is drying up, shorts are being covered, and institutional traders have already begun to buy (if they hadn't, there wouldn't be a higher low).
Yes, "large volume" attracts attention. Bells go off. But it's no predictor. It is rather a descriptor of the states of mind of buyers and sellers. If buying interest and pressure are greater than selling interest, price will rise. Otherwise, not.
Note: those who insist that volume leads or precedes price are not stupid, but they clearly are defining volume in a special way since without a print there is nothing for price to lead. Without a print, one won't even be aware of it. It may be a wish or a hope, but it's not "volume", or at least any sort of volume that one can do something with or for most traders even be aware of.
I strongly suggest that those who are still confused by all this study or at least read up on auction market theory. If one doesn't understand how an auction market works, all of this will most likely forever be a mystery.