"As a specification language, Simplicity allows us to make everything explicit, so that we can mathematically model it, prove the essential properties that we need for our applications, and then encapsulate it, confident that we have a rock-solid foundation for the things we believe about our code."
"Unlike most programming languages, Simplicity expressions are constructed from a series of combinators, which build up expressions from smaller ones. Such expressions represent functions taking some input and mapping it to some output."
"Our goal with Simplicity is to formally specify the semantics of programs, both in terms of what functions they represent, and what computational resources are involved in evaluating them."
"It would be possible, in principle, to formally specify a language which operates like Bitcoin Script or EVM, but the task would be extremely difficult, and the result would be nearly as difficult for anybody to verify."
"Instead, with Simplicity, we defined a small set of basic combinators, each of which reflects a mathematically fundamental way of combining functions. The resulting language’s semantics are so small that they fit on a T-shirt."
"In practice, for things like bit inversion, this code will only be written once, then reused. In fact, we’ve done the writing for you and built it into the language. When writing your own code, you can simply use the shortcut jet_not in place of the above code."
"Eventually, in practice, almost nobody will be writing Simplicity code at all. Simplicity provides a well-defined foundation for blockchain programs, but it is just that: a foundation. The real work will be done in higher-level languages, which compile down to Simplicity code alongside proofs of their correct operation."