I am reduced to the necessity of offering my written but warm thanks, for the valuable present, left for me by your Ladyship– I have read several parts of the Essays with a curious pleasure—several with an entire mental satisfaction: and I have everywhere admired the originality, brilliancy, & power, which,—whether your Ladyship’s positions be questionable or the contrary,—undeniably distinguish your mode of supporting them. It is better to appear arrogant than to be dishonest: & it would be dishonest & disingenuous if I were to conceal the opinion I cannot help entertaining, respecting the extension of finite minds. I cannot honestly say that your Ladyship’s arguments have changed or modified that opinion. If finite minds have not a distinct locality, they must inter-exist & be commingled: if they have a distinct locality, they must have bounds: and bounds pre-suppose extension.
This is an interesting argument.
(1) Either finite minds have a distinct locality or not.
(2) If they do not have a distinct locality, they are not distinct.
(3) If they have a distinct locality, they must have bounds.
(4) If they have bounds, they must be extended.
And, presumably (given that she summarizes the argument as concerned with "the extension of finite minds"),
(5) Finite minds are distinct.
(6) Finite minds are extended.
The obvious premise in need of defense is (2), since place-distinction is not the only way to distinguish, but the premise that in a sense matters is (3), since finite minds do prima facie often have distinct localities -- for instance, we associate my mind with my body and not with the moon. There seems to be need of a distinction or two here, though.
Browning seems to be referring to Lady Mary Shepherd's Essay XI, "On the Immateriality of Mind", in which she argues of sensation that "though it does not occupy space as solid extension, yet it has a necessary relation to space, by requiring space in which to exist" (EPEU, p. 386). Her primary concern is to argue that sensation cannot exist on its own; but it does require that finite minds have a distinct locality, and Shepherd does there at least consider the possibility of attributing extension to the immaterial mind, despite its not being her own view. Browning is certainly right that Shepherd's arguments would not have modified her own view; Shepherd hardly talks about the topic at all.