An absolute truth (sometimes called a universal truth), is an unalterable and permanent fact. The concept of absolute truths - what they are and whether they exist - has been debated among many different groups of people. Philosophers have waded in the muck of defining absolute truth for millennia. For example, Plato believed that absolute truth existed, but that truth on earth was merely a shadow of great forms of absolute truth existing in the universe. Alternatively, many believe in relative truths, where facts may vary depending on the circumstances.