A revaluation of Dee's character and significance came in the 20th century, largely through the work of the historians Charlotte Fell Smith and Dame Frances Yates. Both brought into focus the parallel roles of magic, science and religion in the Elizabethan Renaissance. Fell Smith writes: "There is perhaps no learned author in history who has been so persistently misjudged, nay, even slandered, by his posterity, and not a voice in all the three centuries uplifted even to claim for him a fair hearing. Surely it is time that the cause of all this universal condemnation should be examined in the light of reason and science; and perhaps it will be found to exist mainly in the fact that he was too far advanced in speculative thought for his own age to understand." Through this and subsequent re-evaluation, Dee is now viewed as a serious scholar and book collector, a devoted Christian (albeit at a confusing time for that faith), an able scientist and one of the most learned men of his day. His Mortlake library was the largest in the country before it was vandalised, and created at enormous, sometimes ruinous personal expense; it was seen as one of the finest in Europe, perhaps second only to that of De Thou. As well as being an astrological and scientific advisor to Elizabeth and her court, he was an early advocate of colonisation of North America, envisioning a British Empire stretching across the North Atlantic.