Just to muddy the waters a little more:
If you are looking at a printed photograph, what constitutes normal perspective and field of view depends on the print size and viewing distance.
For example, if you shoot a scene with an ultra-wide lens, print it really huge (40x60 inches), and view it from a couple of feet away, it will match how you saw the scene when you were there. It will also show a very wide field of view.
So a "normal" lens matches your eye's perspective when viewing a "normal" sized print from a "normal" distance.
The example of looking through a camera's viewfinder, and holding the other eye open, is false. It depends on the viewfinder magnification.
If you are looking at a printed photograph, what constitutes normal perspective and field of view depends on the print size and viewing distance.
For example, if you shoot a scene with an ultra-wide lens, print it really huge (40x60 inches), and view it from a couple of feet away, it will match how you saw the scene when you were there. It will also show a very wide field of view.
So a "normal" lens matches your eye's perspective when viewing a "normal" sized print from a "normal" distance.
The example of looking through a camera's viewfinder, and holding the other eye open, is false. It depends on the viewfinder magnification.