Wonder is the conception (imaginatio) of anything, wherein the mind comes to a stand, because the particular concept in question has no connection with other concepts (cf.III.lii.

and note).
Explanation--In the note to II.xviii.we showed the reason, why the mind, from the contemplation of one thing, straightway falls to the contemplation of another thing, namely, because the images of the two things are so associated and arranged, that one follows the other.

This state of association is impossible, if the image of the thing be new; the mind will then be at a stand in the contemplation thereof, until it is determined by other causes to think of something else.
Thus the conception of a new object, considered in itself, is of the same nature as other conceptions; hence, I do not include wonder among the emotions, nor do I see why I should so include it, inasmuch as this distraction of the mind arises from no positive cause drawing away the mind from other objects, but merely from the absence of a cause, which should determine the mind to pass from the contemplation of one object to the contemplation of another.
I, therefore, recognize only three primitive or primary emotions (as I said in the note to III.

xi.), namely, pleasure, pain, and desire.

I have spoken of wonder simply because it is customary to speak of certain emotions springing from the three primitive ones by different names, when they are referred to the objects of our wonder.