If one views probabilities as encoding a state of knowledge, it is absurd
to speak of them as being "unknown", or placing upper or lower bounds
on them, as if one were unsure of one's own state of knowledge.
Kathryn Blackmond Laskey replied:
Are you sure of your state of knowledge? I'm not.
Perhaps we're getting into semantic difficulties here. Suppose we use "state of
information" instead? Whatever problem you are attempting to solve, you must
first lay out all the information you have available. Some of this will be
things known to be true or false; some of this will be real-world data
(measurements of various sorts); some will be merely accumulated experience or
physical considerations telling you that certain things are rather implausible
(e.g., a temperature reading of 100 Celsius just above the surface of a glacier
is highly implausible.) This is your state of information. Any uncertainties
you have are part of this state of information.