Premise is, both in Italian and English, the word I would use.

American Heritage Dictionary - Cite This Source prem·ise (prěm'ĭs) Pronunciation Key
n. also prem·iss (prěm'ĭs)

A proposition upon which an argument is based or from which a conclusion is drawn.
Logic
One of the propositions in a deductive argument.
Either the major or the minor proposition of a syllogism, from which the conclusion is drawn.
Land and the buildings on it.
A building or part of a building.
premises Law The preliminary or explanatory statements or facts of a document, as in a deed.
premises
Land and the buildings on it.
A building or part of a building.

v. prem·ised, prem·is·ing, prem·is·es

v. tr.

To state in advance as an introduction or explanation.
To state or assume as a proposition in an argument.

v. intr.
To make a premise.




--------------------------------------------------
Note added at 7 hrs (2007-06-09 15:27:33 GMT)
--------------------------------------------------

Another option would be
Therefore, after premising...........perceptions, we now proceed to