Testator reaching out from the grave

I am looking forward to my class in succession. My main text will be Paras's Civil Code of the Philippines, Annotated, Vol. III, 2013 Edition. As an aside, why Paras's and not Paras'. Because Strunk says it should be that way.

My reference will be Balane's Jottings and Jurisprudence in Civil Law (Succession), 2010 Edition.

Article 900 of the Civil Code of the Philippines, first paragraph,  says:

If the only survivor is the widow or  widower, she or he shall be entitled to one-half of the hereditary estate of the deceased spouse, and the testator may freely dispose of the other half.

If there is already a widow or widower then the testator is already dead. Right? How then can the testator freely dispose of the other half?

Update: OK I take back what I said about Paras's and not Paras'. Paras' it should be for me from now on. Strunk is kind of outdated already but should be a good start for everyone. See the discussion of Steven Pinker here.