Presidential candidate Rick Santorum suggested GOP rival Ted Cruz is too soft in his opposition to marriage equality.

During an appearance on Simon Conway's Iowa radio show, Santorum was asked about Cruz's recent remarks about the need for conservatives to unify around one GOP candidate.

“Look, I'm very proud of the conservative record I've put together,” Santorum answered. “There's no one who's fought more on moral and cultural issues. I'm not a Libertarian. There are people in this race that want the states to decide whether there should be same-sex marriage or polygamy or marijuana use. I don't believe that. I don't believe that the states have the right to redefine something that's not capable of redefining.”

“For me,” he continued, “when you say the states have the right to define marriage, it’s like saying, well, the states have the right to redefine the chemical equation for water, it can be H3O instead of H2O. Well, the states can’t do that. Why? Because nature dictates what water is, nature dictates what marriage is, and the states don’t have the right to violate what nature has dictated.”

Santorum is widely known for using creative metaphors to illustrate his opposition to marriage equality. During the last presidential election cycle, he decried the institution because paper towels are not napkins and beer is not water.

(Related: Rick Santorum opposes gay marriage because paper towels are not napkins.)