When we say thank you, we are acknowledging that we have received a gift. We are expressing gratitude for something that came to us freely, not something we have worked for. To get a bit philosophical about it, by saying "Thank You!" we are acknowledging our inter-dependence; we are naming our need for unearned gifts like water, air and love. Seen this way, expressing our gratitude becomes a way of acknowledging that we are part of the web of life which sustains all that we are, all that we can be and all life on the planet!