Jose Canseco hits season homer number 40 during the first inning of the A's games against the Kansas City Royals on Sept. 18, 1988, in Oakland. Canseco became the first player to hit 40 home runs and steal 40 bases and he led the A's to the first of three straight AL pennants. Bill Beattie/AP
Jose Canseco rests after getting his 40th stolen base against the Milwaukee Brewers on Sept. 24, 1988 in Milwaukee. In 1988, he led the majors with 42 home runs and 124 RBIs, and he was a unanimous choice as MVP. Steve Pyle/AP
Barry Bonds watches his 40th home run of the season take flight during the game against the San Diego Padres in San Francisco on Sept. 16, 1996. Eric Risberg/AP
Barry Bonds picks up second base after stealing it for his 40th steal of the season during the game against the Colorado Rockies at Coors Field on Friday, Sept. 27, 1996. David Zalubowski/AP
In addition to joining the 40-40 Club in 1998, Alex Rodriguez won his second Silver Slugger Award. Jonathan Daniel/Allsport via Getty Images
Sluggin' and slidin'. Ben VanHouten/Seattle Mariners
Alfonso Soriano poses with Stan Kasten, team president, left, and Mark Lerner, principal owner, right, with a plaque honoring his 40-40 achievement. Nick Wass/AP
This begs the question: Is it really stealing if you're allowed to keep the 40th base?