"Negation" to define positives

Presence is the negation of absence.
Generally presence is a small set and absence is a jumbo set when compared to the former.
For instance

Let us consider defining "Being happy". Happiness is considerably difficult to define autonomously.
Happiness can have varied definitions : Bliss, State of delight, Being in great spirits; But these are are vague and needs further expansions and explanations we will end up with a recursive definition for it.
Instead 'Unhappiness' is easy to define and quantify ..
For instance for me
Unhappiness = { Being unwell , Failing , After a fight , ... }

Now happiness can easily be defined a negation / absence of unhappiness.
This again is a vague description because happiness and unhappiness are not just 2 elements of a binary system are certain fuzzy states in between. For example there are certain times when we are neither happy nor unhappy. However the previous definition does not account for this.

There are many instances in the vedas and other scriptures where the presence is defined as the negation of absence good is said to be the negation of bad.
Here I quote 2 such instances:
Advaita ... ( flicked from http://www.wie.org/j14/shankar.asp?page=2 )

why is it called "nondualism?" God is one, isn't it? Why is the word "advaita" being used? Advaita means not two. Why did the sages not say "one?" Why did they say "not two?"...to come back to the point, the word "advaita" is used to indicate not two! And the reason why is because the mind functions in a very linear way, from point A to points B, C, D, E, F and so on in a straight line—are you with me so far? Therefore, the moment you say "one," it means that there are two, three, four, five, six, seven, eight and so on and so forth. The moment you say "one," it means the possibility exists of two. One has got meaning only with relation to the other numbers; otherwise it has none. And the moment you say "one," two has already penetrated into it. That is why they don't say "ekant." They say "NOT TWO!" And NOT TWO means what? That the many has disappeared. But this is only indicated by a process of negation.

Swades...

Swades movie ... Pal Pal song... has a phrase " Man se ravan jo nikale . Ram uske man mein hai ".Ram is the good. Ravan is the evil. Ram 's existance is defined as the absence of ravan. Meaning we inherently become good when we root out the bad within us.