A phenomenon is that which is observed. A noumenon is that which is.
The two need not be the same. Just because you observed a yellow umbrella, does it mean that the yellow umbrella is? Are you sure of the existence of the yellow umbrella? Maybe you observed it in a dream. If the yellow umbrella from your dream (which you took to be the truth when you were in the dream) is not, what makes us so sure that the yellow umbrella that you observe in the “real” world, is?
Philosophers have debated this question for centuries. The philosophy of the scientific method is inextricably linked to the above question. How? Read on …
A Bolt of Noumena
Consider the following example. In a thunderstorm, I observed a bolt of lightning from my window. To be more precise, I perceived certain sights and sounds, which together trigger the recognition of “lightning” in my mind. Is my belief in the lightning actually having taken place justified? Is the lightning a noumenon?
I believe that for some time before the lightning took place, wind was causing static electricity to build up in the clouds. This caused the air around it to ionize, thus increasing the conductivity of this air. The excess (or deficiency) of electrons found it easy to travel this ionized pathways, thus producing an electronic flash discharge. Lightning!
Is my belief in this mechanism justified? Even more fundamentally, is my belief in the existence of the most important ingredient of the above explanation — the electron itself — justified? Is the electron a noumenon?
Noumena and Theories
Our belief in things such as lightning, electrons, molecules, light, force, energy, etc. as objects which have actual existence — as noumena — is philosophically suspect for the same reason our belief in the yellow umbrella is philosophically suspect. Nonetheless, our belief in these things, formalized in mathematical representations called theories, allows us to explain, predict and even control many real world phenomena.
Even though we may never know the true, essential character of the universal noumenon — call it the universal computer, nature or God — we hope that the theories that we build of real-world phenomena and our imagined reasons behind them are in some way taking us closer and closer to the ultimate truth. If one exists.