life's greatest quest. Nobody
knows what love is, though (nearly) everybody thinks they do. This is just a little of what I think:
Yes, love is real. No, it's not a set value, thus;
That which one person might consider love another might consider the act of just liking some one in a romantic way
Quite so, and a difficult thing to remember when we're in the throes of it all.
Love is Fire. So love has the colours of fire (you should know the colours of fire; the blue of Selenium, green of Thallium, the red of Strontium); but all fire consumes. Love is the reason for life, but love can hurt so much the only way out may seem to be to relinquish it. It never is. We always survive, even if we don't want to.
Is it possible to define 'love'?
i don't think so. (And you are
asking what we
think.) But the effort is part of what makes us human.
Are humans designed to love [?]
i don't believe humans are designed. Full stop. If you do, that's a deciding factor in your view of ... well, not just this question, but everything.
is [it] unreasonable to say that we ourselves initially construct it, without at first loving, then become incapable of destroying this manually built love, thus rendering it 'true' love?
No, not unreasonable to say construction can happen. If i understand you correctly your question is
about construction. It's a fundamental problem. In our youth we may construct an idea of "love" itself, without experience, without "at first loving". Then, as throughout our lives, we live at risk of constructing an image of "love" and looking for someone to fulfil it. Anyone who is looking for a lover who is "tall", "slim", "witty", "generous", "long-haired", "brunette", "wealthy" (ad nauseam) is guilty of this self delusion. It's just a filter. We seldom fall in love with people who match our criteria anyway. Our greatest loves are the most unexpected.
Ultimately the only thing that matters is what YOU
think. Secondarily, what the person you love thinks.
Sorry if this is a "long winded answer" with "often contradictory conclusions", but you did ask. And it's a fascinating question.