This is a nostalgic account of how two certain key results in modern theoretical physics (prior to World War II) can be expressed concisely in the language of quaternions, thus suggesting how they might have been discovered if Hamilton’s views had prevailed. In the first instance, biquaternions are used to discuss special relativity and Maxwell’s equations. To express Dirac’s equation of the electron, we are led to replace the complex number / by the right regular representation of the… Expand