The best example MH gives is a symptom of a disease. The pock marks show themselves and in so doing indicate the occurrence of a disease. Note that appearance is not semblance. Instead, the pock marks shows themselves as just what they are, pock marks. They refer to or indicate the disease.
Appearance is neither illusion nor distortion.
The symptoms of a disease bear an intelligible relation to the disease the disease explains the symptoms. The wind bears an intelligible relation to the change in barometric pressure again, the pressure explains the wind. Watch for this in the text and don t let it get you confused. So again, the formal concept of the phenomenon is a generic concept, covering all more specific concepts of types of phenomena. That is, something is a phenomenon in the ordinary sense, if we experience it by means of the five senses.