ABSTRACT
This chapter provides evidence that, before the last few months of 1888, Francis Galton had never used the word correlation in a mathematical sense and had never used the word “co-relation” in any sense. This evidence negates claims by multiple other historians in regards to where and when Galton first used those words and first conceived of the concept of mathematical linear correlation. Such evidence includes his first use of the word correlation in papers that predate his 1869 book titled Hereditary Genius (uses that it seems no other historian has ever mentioned). An analysis of his 1874 book English Men of Science reveals that his statement there about head-size and energy levels was clearly not mathematical in nature. A deep-dive into his book Natural Inheritance (written in mid-1888) shows that neither the word nor the concept of mathematical correlation appeared in it, despite statements to the contrary by other historians. Also discussed is how, pre-December 1888, he consistently used the word “relation” where he would have instead used the word “correlation” after his December-1888 announcement of his discovery of mathematical correlation. A close read of two papers he published in early 1888 reveals that he was frustrated by his inability to quantitate the degree of interdependence between measurements of closely associated biometric variables.
