The Napoleonic Wars (1803–1815) are part of the novel's hidden background. Calvo, quoting Roger Sales, says "Mansfield Park" can be read as a Condition-of-England novel that 'debates topical issues such as the conduct of the war and the Regency crisis'. Duckworth (1994) believes that Austen took the landscaping symbol from Edmund Burke's influential book, "Reflections of the Revolution in France" (1790). Burke affirmed the beneficial "improvements" which are part of conservation, but decried malign "innovations" and "alterations" to society which led to the destruction of heritage. Duckworth argues that "Mansfield Park" is pivotal to an understanding of Austen's views. Estates, like society, might be in need of improvements, but the changes allegedly advocated by Repton were unacceptable innovations, alterations to the estate that, symbolically, would destroy the entire moral and social heritage. Austen, aware of the fragility of a society uninformed by responsible individual behaviour, is committed to the inherited values of a Christian humanist culture.