Defining Love

I often sign "I Love you" to my son although I know he is too young to understand what it means. But it got me wondering how when he was old enough to communicate do you define "love"? It's hard enough to define it as an adult to another adult... but to a child who is just learning new concepts how do you define it? How do you explain the difference between the love a parent has for a child and the love a parent has for the other parent? Do you simplify the definition of love as affection towards another person? That would leave you wide open for the child to ask "why?", Why do you show different degrees of affection for one person than another? How is love or affection measured?

I'm sure I'll figure these things out and I'm sure I'd have Amy's help with it as well. It's just something I've been thinking about lately as a new parent. I'm sure every new parent faces similar questions like that. I found it interesting to consider nevertheless.