In thermodynamics the temperature of a physical system is defined
*empirically* in terms of a thermometric property of a physically
realizable device called a *thermometer*. One of the properties of this
thermometer is that it must be of negligible size compared to the
system with which it is put into contact.
That requirement should put the question to rest; no thermometer can be
constructed that is small with respect to a collection of fifty
particles. Temperature is not a useful quantity for treating such a
system since it cannot be measured.
One can certainly *assign* a temperature to such a system simply by
choosing another definition for temperature, but would it be of any
utility to do so? As Descartes said just before vanishing: "Non
cogito."