Always give the link.
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Undoubtedly there is a right way of reading, so it be sternly subordinated. Man thinking
must not be subdued by his instruments. Books are for the scholar’s
idle times. When he can read God directly the hour is too precious to
be wasted in other men’s transcripts of their readings.
[link]
be is subjunctive here.
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Undoubtedly there is a right way of reading, so it be sternly subordinated.
reads, IMO:
Undoubtedly there is a right way of reading, so that it be sternly subordinated.
Undoubtedly there is a right way of reading, so that/in such way that it should be sternly subordinated.
or, even simpler, but a bit less exact:
Undoubtedly there is a right way of reading, in such way that it is sternly subordinated.