Fed policy is an underappreciated uncertainty, he said. Mr. Sri-Kumar is not convinced that growth will be strong enough for interest rate cuts to be taken off the table.

“When they say they’re going to stand pat in 2020, I don’t have any reason to believe them,” he said.

Investors may be ignoring such unknowns but also some important knowns. A couple that Mr. Sri-Kumar mentioned are stagnant wages and a recession across American manufacturing industries.

Thomas Atteberry, co-manager of the FPA New Income fund, is another growth skeptic.

“Stocks are a leading indicator,” so the rally “is telling you things are getting better,” he said. “But I don’t see earnings or economic data telling me we’re going to have a significant reversal of fortune.”

James Stack, editor of the InvesTech Research investment newsletter, is similarly perturbed by signs of persistent lethargy. He pointed out in a recent issue that the index of leading economic indicators, a widely followed measure that bundles several pieces of data believed to predict economic activity, has been stagnant for more than a year, bringing it “worryingly close,” he said, to a reading that might herald a recession.

It may seem as though investors are too positive today, but Kate Moore, head of thematic strategy for the global allocation team at BlackRock, says instead that they were too negative yesterday.

“We think in general the market had become far too pessimistic,” she said. “A few months ago, coming out of the summer, when everyone was increasing recession probabilities and calling for the end of the world, we were adding risk. We thought the market was misreading the potential for a meaningful slowdown.”