It is inaccurate or impossible to define something by itself.
It is not accurate to define something or quantify it without other sources. For example defining the word five by saying its value is 5.
This means that when defining the universe (such as the beginning of time) by using logic contained by the universe, there is no way of telling if that is correct or not. This is because the universe governs logic.
口Needs Logic and further explanation.