Meaning that e.g.
1) if the pilots' yokes/sticks are being pulled and
2) if the altitude based on gps and/or air pressure and/or radar is decreasing and
3) if the speed registered by the airspeed probe is high respectively increasing and
4) if the fuel being used by the engines to keep or even increase the speed is very low and
5) if the G-force registered by <some sensor, if it exists?> is lower than usual (neutral or even negative?)
6) etc... (anything else excluding AoA?)
...then the airplane is mooost probably "going down", even if the AoA says the opposite.
As the MCAS auto-trim has apparently a big potential impact on how the airplane flies (surfaces on the tail are big and their angle can move a lot), it should therefore not rely on just 1 (or even 2 duplicate) lonely sensor(s) but on multiple types that provide multiple point-of-views of the aircraft's situation to then abstract/determine/confirm the current high-level situation (in this case "is the aircraft going up or down?") and only after such result to react/take countermeasures to save the aircraft respectively help the pilots and/or lower costs for the flight.
If this is not totally wrong, is this (the total integration of all sensors) how Airbus did it with their super-automated systems like e.g. their side-sticks/joysticks just telling the airplane what pilots "want"? (meaning, did they start already from scratch creating a totally integrated system, if they did create such an integrated system?) (not sure about how automated the new Boeing airplanes are, so I did not mention them...)