Spinoza's Ethics: III.P32 - Imitation

Si aliquem re aliqua qua unus solus potiri potest, gaudere imaginamur, conabimur efficere ne ille illa re potiatur.

If we imagine that a person rejoices about something which only one (person) is able to possess, we will try make sure that no one possesses that thing.

DEMONSTRATIO: Ex eo solo quod aliquem re aliqua gaudere imaginamur (per propositionem 27 hujus cum ejusdem I corollario) rem illam amabimus eaque gaudere cupiemus. At (per hypothesin) huic lætitiæ obstare imaginamur quod ille eadem hac re gaudeat; ergo (per propositionem 28 hujus) ne ille eadem potiatur, conabimur. Q.E.D.

From this alone we imagine that because someone rejoices about some thing (by IIIP27 with IIIP27C [Empathy]) we will love that thing and desire to rejoice in it. But (by hypothesis) we imagine due to that person rejoicing in the same thing will hinder this joy; thus we will try (by IIIP28 [Following Beliefs for Power]) so that no one might possess the same thing.

SCHOLIUM: Videmus itaque cum hominum natura plerumque ita comparatum esse ut eorum quibus male est, misereantur et quibus bene est, invideant et (per propositionem præcedentem) eo majore odio quo rem qua alium potiri imaginantur, magis amant. Videmus deinde ex eadem naturæ humanæ proprietate ex qua sequitur homines esse misericordes, sequi etiam eosdem esse invidos et ambitiosos. Denique si ipsam experientiam consulere velimus, ipsam hæc omnia docere experiemur præsertim si ad priores nostræ ætatis annos attenderimus. Nam pueros quia eorum corpus continuo veluti in æquilibrio est, ex hoc solo ridere vel flere experimur quod alios ridere vel flere vident et quicquid præterea vident alios facere, id imitari statim cupiunt et omnia denique sibi cupiunt quibus alios delectari imaginantur; nimirum quia rerum imagines uti diximus sunt ipsæ humani corporis affectiones sive modi quibus corpus humanum a causis externis afficitur disponiturque ad hoc vel illud agendum.

We see thus since the nature of humans is mostly to be so arranged so that they pity those to whom it is bad, they are miserable and to whom it is good, they envy and (by IIIP31 [Confirmation Bias]) the greater the hatred for whom they imagine to possess the thing which they love the more. Next we see from the same property of human nature from which it follows that humans are merciful, also follows that they are envious and ambitious. Next if we prefer to consult experience itself, we will experience that it teaches all these especially experience if we attend to prior years of our life. For children since the body of them is just as if in constant equilibrium, from this alone we experience (they) laugh or  cry because they see others laugh or cry and meanwhile they see others do something, they immediately desire to imitate it and next they desire everything for themselves by which they imagine others to be pleased; too much we have said because to use the images of things are the modifications themselves of the human body or modes by which the human body is affected by external causes and is disposed for doing this or that.