Consider for a moment the rantings of two recent Americans who committed violent suicide, taking others with them to their deaths.

One was the software engineer who crashed his small plane into an Internal Revenue Service building in Texas, destroying the building and sending 200 workers running for their lives. He had left a farewell screed that attacked the IRS, bank bailouts and the “thugs and plunderers” who run America’s corporations. He wrote: “I have had all I can stand. I choose not to keep looking over my shoulder at ‘Big Brother’ while he strips my carcass.”

The other man, an electrical engineering graduate student at San Jose State University, parked his car near the Pentagon, walked toward its entrance, pulled out two 9 mm semi-automatic weapons, and began shooting at police officers at a security checkpoint. They returned fire. He was killed and two of the officers suffered superficial wounds. For several years, according to The New York Times, he had been posting rambling lectures on the Internet, raging against what he saw as a totalitarian federal government that mishandled monetary policy, public education and private property rights.

If those wild, paranoid charges and conspiracy theories sound familiar, it’s because of the new communications environment, with its constant flow of unverified “information” in blogs and Web sites. False and fanciful theories often appeal to individuals who have lost the ability to see the difference between truth and mere speculation.

The so-called Truth movement, which hounded the Bush administration, fostered the idea that federal officials or agencies either knew in advance or actually helped perpetrate the Sept. 11 terrorist attacks in New York and Washington. Adherents include otherwise intelligent people and comprise liberals, conservatives and libertarians. They deny that they are conspiracy theorists and call themselves “Truthers,” “9-11 skeptics” or “truth activists.”

The Obama administration has to contend with the flourishing “Birther” movement, a group of theorists and lawyers devoted to proving that Barack Obama is not eligible to be president of the United States. They claim that his birth certificate issued in Hawaii is a forgery and that he actually was born in Kenya or Indonesia.

Belief in obscure, outlandish theories is nothing new. A recent survey found that 34 percent of the American public believes in UFOs and 24 percent believes in witches.

The conservative talk-show host Michael Medved recently complained that the “crazy nutburgers” are making the conservative movement appear weird and crazy. Possibly as a humorous twist, he suggested that the Birther theories might be part of a great conspiracy to make conservatives disgrace themselves.

The solution is good, straight thinking in an era of hard times, cultural upheavals and terrorist threats. No need to get paranoid about paranoia in others. We’ve been through such things before, and we will again.