Before we proceed to the next topic, while still contemplating single-input logic gates, we might ask ourselves if there are any special pull-up vs. pull-down considerations when using BUF or NOT ...

Also, that we are working with trusty digital logic devices (as opposed to their wibbly-wobbly analog cousins). Also, that we are working with logic 0 and logic 1 values of 0 V and 5 V, respectively.