 Popper’s other explanation of why ad hoc hypotheses were regarded with suspicion was that they ran counter to the aim of science, which for Popper included the proposal of theories with increasing empirical content, viz., increasing falsifiability. Ad hoc hypotheses, for Popper, suffer from a lack of independent testability and thus reduce (or at least fail to increase) the testability of the theories they modify (cf. above). However, Popper’s claim that the process of modifying a theory ad hoc tends to lead to insufficient falsifiability and is ‘unscientific practice’ has been challenged (e.g., Bamford 1993: 350). 