• There are two types of quality: (1) primary and (2) secondary. Substance is primary quality, which can be described as the property of any particular sub-stance. Secondary quality is the effect this substance causes in our mind. Some philosophers, like Berkely, proposed that there are only secondary qualities.
• Quality is the basis for stating that things are similar or dissimilar. Quantity is the basis for stating that things are equal or unequal.
• Mathematics is based on quantity; however recent developments have found ways to describe quality in mathematical models (Statistics, Fuzzy Logic).
C. QUALITY AND SENSE.
Probably the most important thing about quality is its relationship with our senses. It is not easy to distinguish between the primary and the secondary quality. Pri-mary quality, as a characteristic of the substance would probably be "objective". But if we use our senses to determine a certain quality, it is unavoidable that dif-ferent people feel a different "secondary quality" even if the "primary quality" is the same. Eskimos most probably have different understandings of a warm day than Africans. This is the reason humans have introduced exact definitions of qualities and have tried to describe qualities by using quantities. This was necessary for bet-ter communication between individuals; it also deleted a great portion of uncer-tainty. Unfortunately, it is not easy to define quantitative measurements for all qualities. In this case, it is still necessary to use our senses to describe what we feel with words, with music, with drawings, etc. Such description is indeed subjective since different people have different perceptions.
D. HOW IS QUALITY DEFINED IN BUSINESS?.
In business we take a more practical approach to quality, although the same prob-lems exist among quality, quantity, and sense. Oftentimes, these issues are over-come by defining quality as "customer requirements" or as "fitness for purpose".