Without the invention of the microscope, the cell theory would not have been possible.
I would have to say that this statement is most likely inaccurate. Let’s envision a very unlikely scenario. Let’s say that even though the human race was able to produce electron microscopes there was something wrong with the optical nerve in our head and we could not process magnified images. Under those unlikely circumstances, it would be difficult for me to understand that there is no other way for us to discover the cell theory. Let me give an example. There are no truly eye-witness accounts to 9-11 because everyone that really knew what was going on died. (i.e. the passengers in the planes and the terrorists themselves). Even though we lack first-hand accounts of what actually happened we were able to piece together what happened that day. If we lacked the visual acuity to process magnified images I believe that we would still be able to discover cell theory the same way that we discovered black holes. It is impossible to see a black hole, hence the black part in a black hole, because the collapsed star’s gravity is such that it will not even let light escape its gravitational pull. Yet we were able to discover and will soon be able to study them the effect they have on surrounding objects. It would be the same as the cell theory. If we were not able to see them, we could still discover and study them through the effect that they had on their surroundings or by some other yet unknown means.
Pruitt, N. L., & Underwood, L. S. (2006). Bioinquiry: Making connections in biology (3rd ed.). Hoboken, NJ: John Wiley & Sons, Inc.