Science of politics

In the passage in his History of England that Rankine objected to, Macaulay had been making a point about the science of Politics ... 

The oracle who is always consulted and cited on this subject, is the celebrated Montesquieu. If he be not the author of this invaluable precept in the science of politics, he has the merit at least of displaying, and recommending it most effectually to the attention of mankind. Let us endeavour in the first place to ascertain his meaning on this point. 

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