William Ernest Johnson (18581931) was a renowned British logician and economist andalso a fellow of King''s College Cambridge. Originally published in 1924 this book forms the third of a three-volume series by Johnson relating to ''the whole field of logic as ordinarily understood''. The series is widely regarded as Johnson''s greatest achievement making a significant contribution to the tradition of philosophical logic. This book will be of value to anyone with an interest in Johnson''s theorie