Rod1, but how close did you come to those other aircraft that you never saw today?
I suspect you don't fly with a TCAS/TAS because if you did you would understand that my question isn't borne out of sarcasm. You didn't spot all the other aircraft out there, because no-one does.
PPRuNe Radar, what you say is basically correct but the limitations of TCAS/TAS equipment are outlined in the instruction handbooks and the Flight Manual.
I have to agree with IO540, sometimes pilots are obliged to make a captaincy decision based on insufficient information.