Post hoc ergo propter hoc

From Wikipedia

Post hoc ergo propter hoc (Latin: “after this, therefore because of this”) is a logical fallacy (of the questionable cause variety) that states “Since event Y followed event X, event Y must have been caused by event X.” It is often shortened to simply post hoc fallacy. It is subtly different from the fallacy cum hoc ergo propter hoc (“with this, therefore because of this”), in which two things or events occur simultaneously or the chronological ordering is insignificant or unknown. Post hoc is a particularly tempting error because temporal sequence appears to be integral to causality. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection.

he following is a simple example:

The rooster crows immediately before sunrise;
therefore the rooster causes the sun to rise.


The form of the post hoc fallacy can be expressed as follows:

  • A occurred, then B occurred.
  • Therefore, A caused B.

When B is undesirable, this pattern is often extended to the inverse:
Avoiding A will prevent B.


  • “I can’t help thinking that you are the cause of this problem; we never had any problem with the furnace until you moved into the apartment.” The manager of the apartment house, on no stated grounds other than the temporal priority of the new tenant’s occupancy, holds that the tenant’s presence has some causal relationship to the furnace’s becoming faulty.
  • The Brazilian footballer PelĂ© is said to have blamed a dip in his playing performance on having given a fan a specific playing shirt; after getting the shirt back, his performance recovered. Thus, he said, the loss of the shirt was the reason for his dip, and its return was the cause of his recovery. (It was later discovered that the shirt that was returned to him was not, in fact, the one he had given up.)
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About Dr Bode

Retired anesthesiologist. Little league shortstop and team MVP 1956, Newspaper delivery boy of the year at Long Beach Press Telegram 1959. St. Anthony High School Valedictorian 1964. Long Beach State University, Certificate of Excellence in General Chemistry. Long Beach State golf team 1967 - 1968. Graduate, UCLA School of Medicine 1972. Club Champion at Stevens Point Country Club, Wisconsin 1977. Chairman Department of Anesthesia, St. Michael's Hospital, Stevens Point, WI. Certified ACLS Instructor. President, Mendocino Lake County Medical Society 2002 - 2003. Disabled due to phlebitis with palpitations and arrhythmias 2005. Cardiovascular research 2005 to present. Member, American Heart Association, Heart Rhythm Society, California Society of Anesthesiologist, American Society of Anesthesiologists. President Willits Garden Club 2013 - 2015, Director, 2015 - 2017 Mendo-Lake District Garden Clubs

2 thoughts on “Post hoc ergo propter hoc

    • One important issue with ‘post hoc’ involves the interpretation of EKG potentials called the P, QRS, and T waves.

      Doctors teach that cardiac cell action potentials generate EKG waves. Atrial depolarization causes P waves and ventricular depolarization causes QRS waves. Finally, repolarization of the ventricles cause T waves. Moreover, the ventricle repolarization time is very long, about 100 times longer than other muscle repolarization time.

      It is my opinion that EKG orthodoxy is a ‘post hoc’ misunderstanding of the EKG. Research by Findl and Kurtz in 1977 observed that motion of electrolytes from pulsed blood flow from artificial mammalian hearts generates EKG like signals.

      It seems to me that blood flow generates EKG potentials.

      Thus, atrial contractions generate blood flow, which produces P waves. Next, ventricular contractions generate blood flow, which produces QRS waves. Finally, contractions of the aorta and pulmonary artery generate pulsed blood flow motion, which produces T waves.

      Electrical or neurological events move FAST, near the speed of light, which blurs the evidence and leads to ‘post hoc’ mistakes.

      It is a challenge to examine data and split details into pieces that make sense. It seems to me that the downward outward isovolumetric bulge of the apex of the heart ventricles causes the Q wave of the EKG.

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