2.1.7. True Goods.

D.1. True Goods: 

I. As an opposition of Imaginary Goods, with expansion of knowledge, the weakness of knowledge is overcome and the truly existing Needs, and truly existing Useful Things are discovered.

II. Goods which serve needs, and have useful properties both of which are actual and freed from misperception. 

Axiomatic Derivation:

8.1. It is immediate from Imaginary Goods and Primacy of Knowledge (See 9 and 10 in it) as the knowledge expands, it weaknesses are mitigated, and as weaknesses of knowledge are mitigated, possibilities increase of True Needs, and True Useful Things constituting Good Characteristics of Useful Things.

8.2. True Need is a need that exists in fact in sense as explained in Needs, and true Useful Thing is a Useful Thing which serves our Needs in fact in sense as explained Useful Things. 

Explanations:

E.1. In contrast to Imaginary Goods, goods which do serve an existing need, and have a capacity to gratify in reality are true goods. Hence, where colour water therapy is imaginary good, an Anti-Allergy tablet from a doctor is true good, and as the need of marriage ritual does not exist, the need of respect and harmony between two partners do exist. So rituals in marriage are imaginary goods, but arrangements to ensure selection of the right partner are true goods.

Reference: Menger, Carl (2004). Principles of Economics, Online edition, The Mises Institute, 2004. (Chapter 01 page 53 footnote)