The strong coupling between the quarks and gluons makes QCD a difficult theory to study.
His meditations on the difficult theory of the point were related to problems encountered in optics, space, and movement; they were published in 1671 under the general title Hypothesis Physica Nova ("New Physical Hypothesis").
The Barnsley manager, Simon Davey, said that the quality of the game demonstrated that the gulf between the Premier League and the Championship was narrowing but, putting aside the undoubted commitment of both teams, that was a difficult theory with which to agree.
This is a rather difficult theory.
It should be clear that Descartes' theory of ideas has been, and continues to be, a difficult theory to pin down.
However, this is a difficult theory to disprove.
The constructive empiricist, in contrast, suggests that the reason a scientist turns to a theory is that experimental design is difficult, and theories are needed to guide experimental inquiry.
Calculations are difficult, fertility theories abound, and the population growth rate has fallen by more than 40%.
For a taut "no-word-wasted" writing style I like AJP Taylor, and to explain difficult scientific theories to numpties like me, then Michael Brooks takes some beating.
Furthermore, in virtue of various technicalities of the definitions, it apparently turns out that Chisholm's account of the meaning of 'he could have done otherwise' is adequate to all the cases that prove difficult for theories such as the ones surveyed above.
