Coming into our solar system, whats known as the Ecosphere or habitable zone includes Mars, Earth, and Venus; the 6, 7, and 8 planets in.

It is said that Earth is a Goldilocks, meaning it is just right to support life. That word, when used in this context, usually connotates that Earth, being so perfectly just right, shows that there must be some intelligent design to it, as opposed to just random.