However, the heuristic value of species recognition is hampered by its reliance on the problematic concept of species.
The standards in force make ample use of the problematic concept of ductility of a structure, which is applicable in the case of plants.
Deep time or geologic time appears to be one of the fundamental and problematic concepts for the understanding of evolution (see, for example, Dodick and Orion 2003a, b, c).
Randomness, because it also deals with probability and predictability, is another problematic concept for biology students, many of whom, using a "street" rather than a mathematical definition, assume that random means "purposeless".
The song was the biggest hit of 1969, an indication that the future remained a problematic concept for many people.
Despite its veneer of neutrality (a problematic concept anyway, of course) the Today programme gives us a very specific take on the world.
In this instance, he tries to explain confusing and problematic concepts in the realm of ethics.
The project of providing "analyses" in this way of especially problematic concepts like those concerning, for example, material objects, knowledge, perception, causation, freedom, and the self, was pursued by Positivists and other "analytic" philosophers for a considerable period (see Carnap 1928 [1967] for some rigorous examples, Ayer 1934 [1952] for more accessible ones).
This invites the objection, raised both by Tennant (1987: 236) and by Boolos (1987: 184) that in certain conspicuous cases there is no a priori justification for commitment to the existence of denotations for these terms, in the case of particularly problematic concepts Φ (such as self-identity).
Rather, it will show how problematic the concepts of authorship and results reporting are in the modern clinical trial.
