The most important for the fulfillment of the "Declaration of Human Rigts' Vow" is the universal respect and practice of human rights.
The "preamble" conveys the fundamental logic of why the document is necessary explaining its motivation.
The word "whereas" is frequently used in legal preambles, in the same sense of other expressions such as: "forasmuch as" or "in comparison with the fact that" or "taking in consideration the fact that" or "in view of the fact that" or simply another habitual word like "since", to compare a subsequent statement with a previous known fact. Thereby (b)