Pitman's Commercial Spanish Grammar (2nd ed.)

by C. A. Toledano

13. Our friends have large stocks but they say the market is looking up (mejorando).

LESSON XVII.
(Lección décima séptima.)

"SER" AND "ESTAR."

=Ser= is used as a true auxiliary, when it forms the passive voice.

=Estar= is an auxiliary when it forms the progressive tenses, as

Estoy escribiendo (I am writing).
Estaba escribiendo (he was writing).

The difficulty in the employment of ser and estar is, by some, unduly magnified. Others give the following rule—

Ser denotes a permanent state. Estar "temporary"

This rule should not be adopted because often it would not apply, as the following two examples will show—

Él es soldado porque se ha alistado por dos años: He is a soldier as he has enlisted for two years.