The Relevance of Intuitions in Experimental Philosophy Surveys

Experimental philosophy (X-Phi) is a novel approach to philosophy, which surveys people’s intuitions in order to support or undermine philosophical theories. It is a major assumption of X-Phi that these surveys accurately capture people’s intuitive responses to philosophical issues. The central purpose of this research is to investigate whether this is a safe assumption. One of the most influential X-Phi surveys discovered a surprising asymmetry in people’s “intuitions” about intentionality (Knobe, 2003). In my project, I distribute the same survey questions but provide a philosophical definition of intentionality to participants in advance. It will be investigated how the survey results change if participants are given something other than their intuitions to rely on. I hypothesize that the responses will be more symmetrical in my survey than in Knobe’s. If this hypothesis is true, this may support the claim that most people rely on ambiguous definitions of philosophical concepts and that X-Phi surveys like Knobe’s are accurate evidence of people’s intuitions. Alternatively, it could be evidence that critically thinking improves consistency. If the survey responses show asymmetry even after defining intentionality, this may indicate that the participants either ignored the definition, have intuitions so strong that they override the definition, or committed a performance error in using the concept of intentionality. In which case, the many uses of survey data in X-Phi may not be accurate representations of people’s intuitions at all, but could be evidence of differences in the use of concepts, i.e., the ways in which people reason

Crustal and upper mantle structure data analysis

Approximately 50 seismograms obtained from the National Geophysical and Solar-Terrestrial Data Center were digitized and analysis of surface wave dispersion was begun

The crustal structure and tectonics of South America

A preliminary crustal structure map and a bibliography of crustal and upper mantle studies for South America are given. Work on the surface wave analysis and tectonic characterizations continues

Application of MAGSAT to lithospheric modeling in South America

Progress in the determination of relations of MAGSAT anomalies to lithospheric structures is reported. The prime emphasis was on a Rayleigh wave study and the determination of both group and phase velocity dispersion

Evaluation of existing knowledge of the tectonic history and lithospheric structure of South America

While data is available on the lithospheric and crustal structure of the Andes region of South America, there is limited knowledge of these aspects of the eastern portion of the continent. For this reason, a surface wave dispersion study of the area was initiated. Long period seismograms were obtained for a tripartite analysis of dispersion. A flow chart of the analysis to be conducted is presented along with a preliminary geologic/tectonic map that was prepared. Efforts to characterize the provinces identified in terms of their geological and geophysical parameters continue

Basement Rocks of the Main Interior Basins of the Midcontinent

The basement underlying the deeper basins in the Midcontinent is not well known because of the considerable thickness of overlying sedimentary rocks. However, gravity and magnetic surveys and sparse wells to basement suggest that deeper intracratonic basins are characteristically underlain by denser and more magnetic rocks than in adjacent areas. This correlation has important bearing on understanding the tectonic development and geologic history of Midcontinent basins. The Michigan basin is underlain by prominent, linear gravity and magnetic highs that extend across the southern peninsula. A recent deep well to basement encountered basalt overlain by red clastic sedimentary rock. The combined geophysical and geological data support the idea that the basin is underlain by a Precambrian rift zone. The Illinois basin also contains prominent gravity and magnetic anomalies. The broad anomalies do not appear to correlate with any specific rock type at or near the top of the basement and may instead reflect intrabasement variation, such as major tectonic boundaries. The more local, closely spaced anomalies outline a complex reactivated rift zone that trends generally northeast through the deepest part of the basin. The Williston basin is another deep basin that is underlain by a linear gravity high. The gravity anomalies continue into Canada where they are associated with granulites and major fault zones that occur near the boundary between the Superior and Churchill provinces. The few wells to basement in the deeper parts of the Williston basin along the gravity high encountered granulites and other high-grade metamorphic rocks, suggesting that a major tectonic boundary similar to that occurring in Canada is present in the basement underlying the basin. The Forest City and Salina basins contain less distinct gravity highs, which occur on opposite sides and are partly obscured by the well known Midcontinent gravity high and rift zone. The remaining basin under discussion, the Arkoma basin, differs from those previously discussed in that it contains a large gravity low, which probably reflects the development of an extremely thick section of sedimentary rocks along the Ouachita structural belt. The Arkoma is, thus, more comparable to the Appalachian basin than to the other basins, which are totally within the craton. The basins of the Midcontinent have apparently not all had the same tectonic development and are probably more complex than generally envisioned. A generalization which appears to be a useful working hypothesis is that intracratonic basins of the continental interior differ from foreland basins and originated by reactivation of older structures during periods of extensional tectonism. Consideration of basin development should take into account the Precambrian as well as the overlying Phanerozoic rocks

Role of crustal melting in petrogenesis of the Cretaceous Water Island Formation (Virgin Islands, northeast Antilles Island arc)

The latest Aptian to earliest Albian (~115 Ma) Water Island Fm in the Virgin Islands contains some of the oldest known arc-related strata in the Greater Antilles Island Arc. Hence, the unit is of considerable significance in tectonic reconstructions of initial subduction parameters along the long-lived destructive plate margin separating the North American and Caribbean Plates. Exposed Water Island strata are bimodal, consisting predominantly of altered dacite and rhyolite (originally called keratophyre; 65-85% SiO2) and subordinate degraded (spilite; 46-57% SiO2). TiO2 content of Water Island basalt averages approximately 0.5%, resembling borderline intermediate-Ti boninite basalts, consistent with low incompatible element abundances and low normalized light rare earth elements (LREE) with respect to Sm. Trace element patterns of the felsic suite, characterized by pronounced negative normalized anomalies for high field-strength elements (HFSE), low Sr/Y, and low absolute rare earth element (REE) abundances, and relatively flat normalized REE patterns, have analogues in plagiorhyolite suites from bimodal Cenozoic arcs, including the western Aleutians, Izu-Bonin, the Kermadecs, and South Sandwich. Relatively low incompatible element concentrations in plagiorhyolites and contrasting normalized incompatible trace element patterns in basalts preclude an origin of Water Island plagiorhyolite through MORB-type fractional crystallization. Compositions are consistent instead with melting models involving partial fusion of amphibole-bearing gabbro at low pressures (within the stability range of plagioclase) in response to introduction of heat and aqueous flux by arc-related basalt melts and associated hydrothermal fluids during transmission to the surface. Truncation of the basalt fractional crystallization trend at SiO2 = 57% indicates evolved island arc basalt (IAB) crystal fractionates were gradually displaced from crustal magma conduits by more buoyant plagiorhyolite melt, and trapped in underplated, sub-crustal magma chambers. Basalts have low (Ce/Ce*)N (average ˜ 0.78), indicating the presence of significant pelagic sediment (0.5 to 1.5% Atlantic Cretaceous pelagic sediment, AKPS). One subunit of relatively high-HFSE plagiorhyolite has (Ce/Ce*)N near-expected values, but another with low-HFSE has slightly lower than expected (Ce/Ce*)N, consistent with a small sediment component. Absence of intermediate andesite from the Water Island Fm is inconsistent, however, with basaltrhyolite magma mixing processes. Consequently, incorporation of sediment by low-HFSE plagiorhyolite is inferred to have resulted from re-melting of arc-related gabbro

Pre-arc basement complex and overlying early island arc strata, Southwestern Puerto Rico : overview, geologic evolution, and revised data bases

The pre-arc basement complex in southwestern Puerto Rico consists of rocks exposed in the Bermeja complex. The oldest rocks are highly serpentinized peridotites that occur in three belts (Monte del Estado, Río Guanajibo, and Sierra Bermeja). These serpentinites were emplaced into a sequence of Jurassic to mid-Cretaceous pelagic chert (Mariquita chert) that contains abundant rafts and blocks of N-MORB-type amphibolites (Las Palmas amphibolite) and tholeiite and associated trondhjemite fractionates (Lower Cajul MORB) also of N-MORB affinity. The rocks are apparently overlain by a younger sequence of pre-arc plateau basaltic and andesitic lava flows (Upper Cajul Formation) that occur in two distinct geographic sequences, one having E-MORB and the other OIB geochemical characteristics. Overlying these pre-arc rocks in western Puerto Rico are northwest-trending Late Cretaceous to Eocene (85 to 45Ma) island arc strata that chronologically overlap later volcanic phases in central Puerto Rico. These western Puerto Rico arc rocks have elevated incompatible element concentrations together with conspicuously shallow negative Nb-anomalies, slightly positive Zr-Hf anomalies, and exceedingly high OIB-like Nb/Zr, all indicative of enriched source compositions. Trace element patterns are reproduced by multiple component mixing models involving highly depleted spinel peridotite (RMM15 to 20) overprinted by small OIB-type (up to ~2%) and pelagic sediment components. Trace element abundances are too high to qualify Atlantic Cretaceous pelagic sediment as a potential contaminant, but mantle-melting models (f=0.25) are consistent with the incorporation of variable proportions of Caribbean Cretaceous pelagic sediment through northdipping subduction of the Caribbean basin. Anomalous two-pyroxene-bearing andesites with extraordinarily high SiO2/MgO compared with normal mantle basaltic compositions, also indicate the incorporation of Jurassic to Early Cretaceous pelagic chert from the Caribbean. The high degree of source enrichment in western Puerto Rico is inconsistent with regional within-plate plume tectonics. Instead, it is inferred that the younger north-dipping western Puerto Rico arc (dating from ~85Ma) sampled an upper mantle enrichment zone generated in the backarc region of the older (125 to ~85Ma) south-dipping arc system in central Puerto Rico