Prabhupāda: The materialistic person, they have only one experience: this cosmic manifestation. Beyond this, they have no other vision. Their senses are imperfect. Just like the astronomers, they have got big, big telescope, many other instruments. They want to see through the eyes how many stars are there, how the planets are moving, and whatever imperfect knowledge they receive, by that little knowledge they advertise themselves as great scientists.
But they do not calculate that, "We are trying to see the stars and planets with powerful binoculars. That means our eyes are imperfect." And what is the guarantee that the instruments which they're using, they are also perfect? Because that machine, that binocular, is also made by a person who is imperfect.
So what is the guarantee that by seeing through binocular or microscope, the conclusion arrived, it is perfect? What is your answer? Your eyes are imperfect, that's a fact. Otherwise, why you are using binocular, microscope? Eyes are imperfect.
Originally your eyes are imperfect. Now, eyes or other senses, it doesn't matter. Sense is sense. So you are manufacturing a machine, some instrument, by the same imperfect senses, then what is the guarantee that this machine, this binocular, if you see through the binocular, the knowledge is perfect? What is your answer?
Devotee: Can't be perfect.
Prabhupāda: Answer? Any one other?
Devotee (2): Perfect knowledge cannot be received with imperfect senses. Only through perfect senses can perfect knowledge be received.
Prabhupāda: Therefore it should be concluded that the so-called scientists, astronomers, they are all imperfect, and they are passing on the scientists as learned. So you can challenge them, "What is the guarantee that your knowledge is perfect?" Actually it is not. They do not know how the stars are moving. They are always imperfect, simply putting some theories. They say all this, Darwin's theory and this theory, that theory. They are simply speculating on imperfect senses, and therefore they're cheating, because the conditioned soul has got a tendency to cheat others.