The hows of why and the whys of how

0. How come how come? This paper sets out to investigate a curious how-why alternation, where how is construed as causal rather than manner. English, for one, provides an illustrious example: (1) a. How come Akiu left without saying anything? b. How is it that Akiu left without saying anything? Both (1a,b) are to be understood as a causal question, with how patterning with why and behaving more like a matrix predicate. However, this sort of construal is not productive enough in English to reveal the ins and outs of the how-why alternation. Chinese how, on the other hand, provides a full spectrum of interpretive possibilities such that we are able to piece together a clearer picture. Let's start with a brief preview of some interesting properties of zenme, a Chinese how, which has three types of interpretation: One is manner, which can be further divided into two subtypes, i.e., the method reading, as in (2a), and the style reading, as i