That assumption is:
By today's standards and with today's technology, this or that endeavor is not possible.

Often times the general vagueness of these hidden portions of statements would lead listeners to believe that this or that will never be possible, no matter how much further our technology develops.

In most cases it is not the intention of the expert to make things look like this but it is still sloppy considering what influence authorities have upon people who, laymen or novice, hinge upon every single word.

Be it how much the computer can do to what is possible in outer space, listeners can easily be swayed to induce that this will always be the case.

This ambiguity has been used repeatedly in the past as a ploy to muddy the waters of debate so that a clear answer was not to be found. Argueing a position with this method the proponent, without appearing to do so, leads a listener away from the subject at hand.

Computers, for instance:
There are many experts who believe one way or the other that computers could or could not perform all of the actions that the human brain can. The hidden assumption of, by the present technological standards it will never be possible, can mislead listeners into believing that it could never be possible under all circumstances ie; future history of computing.

One should immeadiatly ask the question;
HOW LONG SHALL THIS PERSIST?

If the rate of technological development over the last 100 years were used as a standard, can we even imagine what information devices will be like in 100 years? What about in a 1000 years? If humans can survive for 10,000 more years, it would take some mighty powers of prediction to say anything about what these things will or will not be able to do.