higher cut-off energy of electronic excitations. The alternative to incoherent particle-hole fluctuations are collective modes of electronic fluctuations, to which we turn next. Part of the spectral weight of particle-hole fluctuations appears in collective modes if the effective interactions are strong enough compared to the kinetic energy. In general a particle hole-fluctuation is characterized by an internal momentum k and a center of mass momentum q , besides other indices which specify the channel of the excitations, for example, density or spin or current or spin-current or inter-valley, interband, etc. A useful limit is obtained from the fact that a bound state of a fermion particle and hole (and indeed particle and particle or hole and hole) has Boson commutation relations. In a bound state, there is no dispersion in energy at any q as a function of k , so the latter index may be summed over. To regard the fluctuations as collective rather than incoherent, one must make sure that the dependence on k is unimportant to do sensible calculations. Also important is the integrated spectra of the collective modes and the incoherent particle-hole spectral weight of fermions for any given channel, is generally fixed by sum-rules. It is sinful double-counting to introduce collective variables, for example spin-fluctuations, and give them the total weight of S ( S + 1) per spin S , and do calculations of their interactions with fermions in the same way that one does for phonons. As we will see later, the frequency dependence of the interaction (with total spectral weight and coupling constant fixed) is of much more importance in determining T$_{c}$ in finite ℓ than for ℓ = 0. The anisotropy of the interaction as well as the details of the geometry of the fermi-surface(s) are also important in determining the irreducible representation favored for pairing. However, essential aspects of finite ℓ pairing, specifically the distinction between the pairing promoted by ferromagnetic and anti-ferromagnetic fluctuations is revealed in a simple model calculation [19] based on a frequency independent and isotropic interaction in a model of a spherical fermi-surface. Consider effective electron-electron interactions of the 17 5. Symmetry of Pairing Interaction from Exchange of Spin-Fluctuations 4. Exchange of collective fluctuations