Recently, there’s been a bit of publicity around Bitcoin, a digital alternative currency that has begun to blossom in popularity. I plan to dedicate future posts to explaining Bitcoin and alternative currencies: what they are and how they work. But before I can do that, I think that it is necessary to talk about money and currency more broadly as a concept, setting forth a few truths about money upon which all alternative currencies are based.So what is money? Simply, it is a medium of exchange, a tool that has been agreed upon by two or more people as an accepted means for holding and transferring value. As with many things in life, it has value exclusively because of our collective agreement that it is valuable. Thinking about it differently, we could say that the value of a US dollar is not physical or material, but rather social.