Love is an irrational desire to nurture. It manifests itself most palpably in a commitment to create conditions in which the loved one can become the healthiest, happiest and most capable person they can be. In short, the purpose of love is to create power in the one loved.
Does this sound like an emotion? No? Well, it isn't intended to. It's intended to make some sense out of what it means to be loved. It's intended to allow us to judge the integrity and value of the words "I love you." It is intended to make a respectful "you love me" the measure of our involvement in the loved one's life.
Loving is an embrace of the purposes of another's will. It is an alignment of our energy with theirs. It is not a surrender of the I to the we ("puppy love"?), but an offering of an I to a you that becomes a we if the offering is elaborated, reciprocated and deepened.
So what about that long list we had earlier? Platonic, romantic, parental, brotherly, patriotic, etc. Simply, it isn't love that changes. It's the tokens of exchange that define the power that can be claimed by the other party to the relationship. Platonic: claims on our attention. Romantic: claims on our sexual expression. Parental: claims of obedience. Brotherly: claims of loyalty. Patriotic: claims of allegiance to causes not our own.
Does this sound poetical? No? Well, that's just not right. There is, indeed, poetry in love, and a genius in that poetry. But it appears only when we learn to separate the business of our relationships from the expression of love. Assertions of power over others control the expressions of their love for us. Love cannot be so controlled successfully, because we cannot see ourselves well enough to know how we need to be nurtured. Love surprises, entices and liberates us from our concern with ourselves. It leads us into opening and grace.
And in the descent, it is the wind at our backs that hollows the obstacles in our path.
In short, love is the key that opens the window to our spirituality.