"It's one of those rough and ready decisions where you try to marry political reality with principle", he said.

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Again, however, the attractive principle faces a murky reality.

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Proponents of this holographic principle believe that all of the complexities of reality contain far less information than common sense would suggest.

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The DanKam, an augmented-reality app for iPhone and Android, works on the same principle.

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What I'm in principle in favour of is people simply recognising geographical reality.

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Yet principle and past suggest that at some point when the gap between actual reality and the vision through the rose-coloured spectacles becomes very large, then the lenses splinter.

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One hard reality is the emergence of transcontinental alliances of liberals and conservatives, undermining the ancient Christian principle that in each geographical area only one bishop should have authority.

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To adapt to this new reality, they need to understand that hitting the backsides of horses was never a value or principle, but simply a way to make carriages run faster.

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