Because ontology concerns what exists, it is unsurprising that the concept of existence comes under scrutiny. There are three noteworthy features of that concept that are generally (but, as always, not universally) accepted within traditional analytic metaphysics. First, existence is all or nothing. You are either in or out: existence does not come in degrees. You might be a bit tall, or a bit bald or a bit boring, but you cannot exist just a bit.