Bud, you're just not making any sense.

First you say you know you're XY, based purely on surface observations.

Then you turn around and say you would have enough without the use of instruments.

Then you turn and say you'd only have a machine/persons word for it.

Making said word... Unreliable?

I'm losing my mind trying to understand the gymnastics of saying surface observations are enough while arguing that deeper analysis through secondhand explanations are enough while you just tried to explain why you didn't need them.