Surviving seventeenth-century Dutch landscapes attributed to major artists now equal in number those attributed to minor ones.
Conclusion
Many attributions of 17th century Dutch landscape to major artists are definitely wrong.
Evidence
Of the surviving 17th century Dutch landscapes, there's an equal number attributed to major artists as to minor ones.
But only a handful of major artists painted in this genre, whereas many prolific minor artists made a living cranking these Dutch landscapes out.
Evaluate
The author is thinking purely in terms of numbers.
She thinks that during the 17th century, major artists would have produced way fewer Dutch landscapes than minor artists would have (since minor artists were cranking these out prolifically, trying to satisfy the insatiable demands of the market).
So let's say for example that major artists created 100 of these paintings, whereas minor artists created 1000 of them.
The author is thinking,
We could call this a Curious Comparison -- how could it be that major artists made less than half of the Dutch landscapes in the 17th century but are attributed to half of the surviving ones?
The author's way of explaining this is, .
We, of course, are tasked with considering Alternate Explanations ....
After all, the ones painted by major artists would be more valuable, presumably, so people would have more incentive to hang onto them. And perhaps they were owned by wealthier people, whose belongings and estates have been better preserved and attended to.
The Dutch landscapes painted by minor artists to satisfy rabid public demand might have been cheap to purchase, painted on cheaper (more degrading) materials, and thus many more of them would have ended up in the garbage eventually.
Goal
Since this is Strengthen, we need to either Rule Out an alternate explanation (Dutch landscapes by major artists were no more likely to be carefully preserved over the centuries than were landscapes by minor artists)
or
Increase the plausibility of the author's explanation (there is reason to believe that a bunch of these 17th century Dutch landscape paintings were erroneously attributed to a major painter)