Final answer:
Belief in proposition A is based on direct sensory evidence, while belief in B involves more complex forms of scientific verification. Both claims can be assessed for reasonableness through the evidence supporting them. The existence of a single objective reality reconciles these observations—the Earth cannot be both flat and spherical; thus, direct and empirical evidence is key.
Step-by-step explanation:
The question of why believing in proposition A ('My mother is real') is more reasonable than proposition B ('The earth is a sphere') involves assessing the evidence and methods of verification for both claims. To determine the reasonableness of belief, we need to evaluate the available evidence and the consistency of the claim with established knowledge. Everyday experience and direct observation affirm the existence of one's mother with immediate sensory evidence. In contrast, the shape of the Earth, while subject to extensive scientific scrutiny, requires more complex forms of verification, such as astronomical observations, physics, satellite imagery, and the effects of gravity. However, this does not necessarily make proposition A more reasonable than B; rather, the types of evidence and methods of inference differ in complexity and scale.
In the realm of philosophical inquiry and the search for truth, the concept that there must be a single, objective reality that explains observations is central. As Carl Sagan highlighted, contradictory claims cannot all be true at the same time. For instance, the Earth cannot be both flat and spherical simultaneously. Philosophical arguments, such as those presented by G.E. Moore, suggest that common sense and the most direct forms of evidence are usually the most reliable sources of belief. This approach can be applied to prove the sphericity of the Earth to a Flat Earth Society member through empirical evidence such as the visible curvature of the horizon, the way ships disappear bottom-first over the horizon, and variations in star constellations with latitude.