Uncertainty
Uncertainty is a lack of knowledge, or lack of accurate knowledge, about something. It is a very common notion. It's possible for one person to have a lot of uncertainty about something while another person doesn't, due to having different amounts of knowledge.
Uncertainty can occur at a very rough level ("About how tall is that tree over there?") or at a precise level ("Does the ruler show 6.7 centimeters or 6.8 centimeters?").
The latter notion of measurement precision was largely undeveloped by the Greek philosophers, though they did have a notion of geometrical exactitude. But it is central to all modern science and engineering.
In Quantum mechanics
While much of science and engineering deals with the ordinary notions of accurate measurement, uncertainty takes on a much deeper and fundamental meaning in quantum mechanics. The wave function of a quantum mechanical system has an intrinsic uncertainty in it. Attempts to interpret that as mere inability to make accurate measurements (so-called "hidden variable" theories), have been shown to be incorrect. The uncertainty of physical systems, as in the Heisenberg Uncertainty Principle, is truly fundamental.
In the Bible
Some people believe that an intrinsic uncertainty is the focus of the Parable of the Wheat and the Chaff, Matthew 13:24-30, which implies that perhaps not even God can initially and easily distinguish between those on his side and those who are against him in this world, or ideas which are good and those that are evil. Others consider this view heretical.
The word "uncertainty" is not mentioned in the KJV of the Bible, but there is this express reference to "uncertainty" at 1 Timothy 6:17 in modern translations:[1]
| “ | Instruct those who are rich in this present world not to be conceited or to fix their hope on the uncertainty of riches, but on God, who richly supplies us with all things to enjoy. | ” |