Substantial progress on some of the most fundamental issues about activity in galaxies requires the analysis of complete and unbiased samples, revealing the physical quantities underlying the observed emission. We propose the first detailed 2.5-200um spectrophotometry of the active galactic nuclei (AGNs) in the Local Universe. This will be done by observing the 12um Active Galaxy Sample, which has been selected to be bolometric flux limited. In fact the 12um flux carries a constant fraction of the bolometric flux for various classes of active galaxies, from blue quasars to dusty Seyfert 2s. The analysis of a representative, unbiased sample to a well-defined bolometric-flux limit, combined with complete multi-frequency data (from X-rays to radio) are both required to address the fundamental issues of galactic and nuclear activity and of the underlying physical connections between the various classes of AGNs towards a unified scheme. For instance, we will be able to address the question if Seyfert 2s are really dusty Seyfert 1s whose broad line regions are completely obscured. Principal component analysis and other statistical methods will be used to find the "dominant correlations" underlying the observed physical properties of AGNs and form the basis of a new classification system - more physically based than the traditional emission-line scheme. Specifically, we propose to observe the 12um AGN Sample with 2.5-12um PHT-S spectrophotometry,60-200um PHT-C photometry and CAM mid-IR imaging. PHT-S will measure very accurately the emission-line spectrum, including high-ionization forbidden lines, H and He recombination lines, molecular transitions, dust features, and the continuum energy distribution. The far-IR photometry will uniquely detect and measure the occurrence and shape of the far-IR turnover providing the best available test of nonthermal models. The broad-band mid-IR imaging will separate nuclear and galaxy luminosities and measure the distribution of hot dust.