About human nature, many thinkers have made a lot of brilliant analysis so as to establish their theory systems, which are related to philosophy of life and society.

许多思想家都对人性提出过精辟论述，以此建构对人生和社会的一系列理论。

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Now theory resembles philosophy perhaps in this: that it asks fundamental questions and also at times builds systems.

理论和哲学的相似之处在于：,它探讨根本性的问题，而且有时也建立系统。

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In theory, these systems would provide easy Internet access to homes, at speeds and prices comparable to that of cable or digital subscriber line connections.

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In theory, the immune systems of the recipients should have rejected the transplanted cells, and among mice that were not treated with the antibodies this was indeed exactly what happened.

ECONOMIST: Breaching the body's defences

An engine running constantly in the hold powered hydraulic and electrical systems that in theory allowed a crew of 4 to do the work of 10 or 20.

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