A purposeful system is free to determine its own goals needed to achieve an outcome. (Ackoff 1971)
Ackoff, R.L. 1971. "Towards a System of Systems Concepts", Management Science, 17(11) USA.
This is the theorectical system science definition. A goal is a specific task achievable in a set time, while an objective is a desired outcome which need to be achieved (or partially achieved) within a time limit. Purposful systems can be given a problem to solve. Humans, and sufficiently complex machines, are purposeful.