In a sense, BS and the option market enable trading in volatility itself.
Specifically, you trade in the estimate of the stock's volatility over the time from now to expiry of the option.
If you don't want to trade options directly to do that (it is cumbersome, as it involves "continuous" delta hedging), you can trade in VIX futures for the same purpose. Or variance swaps.
Specifically, you trade in the estimate of the stock's volatility over the time from now to expiry of the option.
If you don't want to trade options directly to do that (it is cumbersome, as it involves "continuous" delta hedging), you can trade in VIX futures for the same purpose. Or variance swaps.