ZapperZ said:
What model of physics "contradict" one another?
Example: Netwonian dynamics and Maxwellian electrodynamics contradict each other mathematically. This conflict was resolved by making mathematically explicit the underlying core of the conflict, which was that there was another form of dynamics which implicitly underlies the latter, namely SR, and then demonstrating that the former is in fact a limiting case of SR.
This strategy of explicitizing some underlying core and then demonstration of some theory being a limiting case is usually called 'unification', but it is merely one specific form of unification which can and has been generalized in many ways, i.e. the specific strategy is an element in a set of strategies called 'unification'. In any case, the strategy has been used successfully to resolve other analogous conflicts between other theories, but there are a few notorious cases where it has failed so far despite all attempts.
An infamous example is of course the open problem of theoretical physics that QT, in any of its various formulations (including QFT), and GR mathematically contradict each other; the reason why the above strategy seems to fail in this particular case is that the contradiction between the two theories is not merely mathematical, but also actually a conflict in their very axioms and principles, i.e. their underlying core mathematical structures are mathematically incompatible if left as is.
Unification in the face of two incompatible mathematical frameworks is nothing new in mathematics or physics. The correct strategy - obtained by looking at similar resolved cases in the past and making the correct analogy - is then usually to reformulate the axioms and/or principles in a manner such that they all can be cast into a single mathematical framework and then to reconstruct both older theories as special or limiting cases within this new framework.
Most attempts so far, including e.g. string theory and LQG, only try to unify the mathematics of both theories without modifying any of the principles or axioms; it is generally becoming accepted wisdom in the practice of theoretical physicists that this is why these attempts at unification, while partially successful, aren't sufficient to constitute a full and proper resolution of the conflict between QT and GR and therefore are ultimately judged as either failures or merely works in progress.
John Baez, Lucien Hardy and Lee Smolin have each independently described explicit research methodologies for solving open problems in foundational physics. Baez' methodology involves using the mathematical framework of (n-)category theory; see Baez' blog,
this paper or
this book. Hardy has offered a new
constructivist framework which I have described in
this post. Smolin's approach is described in his latest book (see
this thread); if I remember correctly, Smolin's approach is based largely on Einstein's philosophy of physics which explicitizes the difference between constitutive theories and principle theories.