The noted bull has been calling for the index to hit 18,000 since earlier this year.
The United States economy is "going along fine," he said, but the one thing that could derail the market is the Ebola scare.
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"I hope we get this under control. That is my expectation, but that is certainly a wild card out there," Siegel said. "If we do get that under control, I see enough strength in this economy to send the market back up towards year-end."
In fact, there could be a "brighter" holiday season that most are expecting at the moment.
"Let's not discount the lower price of oil, raw materials, that's going to feed into higher consumer incomes, personal income in the fourth quarter," he said.
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As for whether Europe's economic problems will weigh on the U.S., Siegel said he doesn't see it as a major risk at this point.
In fact, he thinks if the euro goes down to $1.20, $1.15, there will be a "big pickup" in Europe's competitive position.