We're returning to your kitchen.
Do you have more plates and bowls than you need to own? (One hint that this may be the case is that you can’t store all your plates in one place but have them stored in multiple locations.)
How many plates do you need? It depends on the number of people in your home, how often you want to wash dishes or run the dishwasher, and how often you entertain.
As you sort and declutter plates and bowls, if you find that you really don't know how many you need, box up half of what you own and move the box to a spot where you can easily retrieve the items if you need them. Leave the remaining items on your shelves.
Over the next four-to-fourteen days, try to only use the items you left for your use. Do you have to wash dishes more often? Is this an inconvenience or does it streamline the process since you aren't tending to more items?
If you want more bowls, bring back half of what you stowed away and live with this new quantity for a few days. Is this enough?
Consider if the time frame in which you're doing this experiment represents what your life is like most of the time. Do you have enough?