Whilst the death of an individual constitutes a mental singularity, it's also worth noting that prior to reaching such an endpoint, different minds not only have different contents, but also possess differently-sized cognitive horizons.
Each cognitive individual has a total mind-map, a fluctuating space of ideas and experiences in memory, linked into a network by the relationships of association, causation and entailment. This space of ideas can be equipped with a metric, which defines the mental distance between any pair of mental items. The distance between two mental items can be defined to be the minimum number of links between those items, taken over all the paths joining those elements in the mind-map. The cognitive horizon of an individual can then be defined to be the maximum distance between any two items in that individual's mind-map. With this concept, we have a precise definition of small-mindedness (and large-mindedness, for that matter).
Following from this, an important question for the philosophy of mind and for neuroscience, is to ask:
Is there an isomorphism at some level between the state of an individual's neuronal network and the state of their mind-map?
If there is such an isomorphism, then an exact brain scan would enable one to read off the state of an individual's mind-map. Conversely, if there is no such isomorphism, then what are the implications of this for the relationship between the mind and the brain?
Cognitive horizon Mind-map