The bull market in stocks, the longest on record since World War II, is so strong that even a 20 percent drop would not derail the long-term viability of the rally, Wall Street's Jeff Saut told CNBC on Tuesday.
By the standard definition, a bear market starts when the falls 20 percent from its bull market high. On the flip side, a bull market begins once the index rises 20 percent from its bear market low.
But Saut, chief investment strategist at Raymond James, thinks the letter of the law should not apply to the current market environment.
"I don't buy it," he argued in a "Squawk Box" interview. If a 20 percent decline were to happen, "it may be a tactical bear market. But it doesn't end a secular bull," defined as a market driven by forces in place for years.
Last week, the bull market that began on March 9, 2009 eclipsed the one that ran from Oct. 11, 1990 until the dot-com bubble burst on March 24, 2000. The S&P 500 has gained more than 300 percent since its low nine years ago.
Saut, whose career in finance has spanned more than four decades, has been touting the strength of the market for years, reiterating on Tuesday his prediction that an upward trend in stocks could last six or seven more years.
However, he also went as far to say that stocks could power higher "maybe into 2027" because he doesn't see any signs of a recession on the horizon.
The economic downturn from the 2008 financial crisis "was so severe and the recovery, up until recently, was so muted that what you've done is elongate the midcycle," argued Saut, who has a history of making prescient calls.
Coming off a 19.4 percent advance in 2017, powered by a late 2016 rally after Donald Trump was elected president, the S&P 500 got off to a smoking 2018 with then-record highs on Jan. 26.
About a week later, Saut said on CNBC that his short-term market model was showing some signals of "potential downside vulnerability" in February.
The S&P 500 then hit a low for the year during the Feb. 9 trading session. Shortly after, Saut expressed near-term caution, but said the bull market remained intact.
Since then, the S&P 500 gained more than 14 percent, closing Monday at a record for the second straight session.