Autonomous systems differ from automatic ones in that they make rational decisions based on knowledge of the current situation. An autonomous system evaluates the courses of action that could be taken in light of current circumstances. In the lift example discussed under Automation, one person gets the same priority as ten.
Like an automatic system, the autonomous system still accepts sensor and user inputs, but operates with more abstract concepts instead of a knee-jerk response to inputs. As with humans, such an autonomous, decision-making system will balance proactive (goal-directed) and reactive (responsive) aspects when making its decisions.
Consequently, the behaviours exhibited by an autonomous system are far more sophisticated than a simple automatic system and this makes a “black box” approach to autonomy unacceptable. Humans are much more cautious of machines that make decisions and are reluctant to place trust in them without first understanding how the they work. So, autonomous systems must be able to expose their reasoning to humans in a manner that is comprehensible – thus establishing trust.
Looking in more detail at autonomy, it becomes clear that it is not simply a black and white choice or condition. Instead, it encompasses systems with a range of capabilities from those entirely independent of human input (i.e. full autonomy), through to systems that provide only timely advice and leave the human to decide and execute the appropriate action (i.e. intelligent assistant).