A long time ago, it was commonly known that the Earth was both flat and that the sun revolved around it rather than the other way around. People believed that women who were too emotional needed to have primitive devices masturbate them to relieve their hysteria. Most diseases, it was believed, could be cured by bleeding out the illness or by placing leeches on the body to suck out the sickness. It was commonly held that if one reduced the taxes on the wealthiest, the savings would trickle down to the rest of us.
Today we can look back on all of this and giggle at our collective gullibility in believing absolute unvarnished horseshit.