Whitehead should not be associated with Russell or Positivism at all except for their joint authorship of Principia Mathematica.
"Following the completion of Principia, Whitehead and Russell began to go their separate ways. Perhaps inevitably, Russell's anti-war activities during World War I, in which Whitehead lost his youngest son, also led to something of a split between the two men. Nevertheless, they remained on relatively good terms for the rest of their lives."They had developed parallel works in mathematics, and it seemed only appropriate that they collaborate as they did in Principia. Equally obviously, though, they had substantial differences in other fields of endeavor.
Of course, being gentlemen, they could disagree amiably. We could also take lessons from that.