In parshat ויגש we find a very interesting use of words in the conversations involving the brothers and יעקב. When יוסף reveals himself to his brothers he asks, אני יוסף העוד אבי חי? (בראשית מ"ה:ג). This is a perplexing question because Yosef already knows that יעקב is alive. Yehudah had previously told Yosef, יש לנו אב זקן. Furthermore, why aren't the brothers able to answer this seemingly simple question? Seforno seems to say that Yosef was asking the brothers how Yaakov had survived emotionally for the past 22 years. The טור suggests that Yosef is asking if Yaakov was still active. Kli Yakar suggests that Yosef's question is a rebuke to the brothers as if to say, "Now you come to save Binyamin because our father might die. Why didn't you think of that when you sold me?" The brothers weren't able to answer this question because of their great embarrassment.
Later when Yaakov is told that Yosef is alive we find similar language in the statement עוד יוסף חי (מה:כו). Initially Yaakov doesn't believe that Yosef is still alive. However, after seeing the עגלות Yosef sent, Yaakov suddenly believes Yosef is alive. In the next Posuk Yaakov is suddenly referred to as ישראל as it says, ויאמר ישראל רב עוד יוסף בני חי. Here again we see the similar formulation of עוד...חי.
This too is very perplexing. How could Yaakov not believe his sons? I would like to suggest he actually did believeיוסף was alive, but was inquiring of his spiritual well being. יעקב is comforted after he sees the עגלות, which רש"י understands to be a symbolism of the דין of עגלה ערופה. The last subject יוסף and יעקב learned together was the issue of עגלה ערפה. In sending the wagons, יוסף was sending a message to יעקב that he was still connecting to Torah, and thereby spiritually alive. The sudden change of יעקב's name to ישראל in פסוק כח answers יוסף's question of העוד אבי חי. He was asking whether יעקב still had רוח הקדש. רש"י (on פסוק כח and see שפתי חכמים ס"ק נ) tells us that his name changed because during the 22 years without יוסף the רוח קדש had left him and had now returned with the knowledge that Yosef was still alive. The Gemara (פסחים קיז.) teaches that someone who is depressed can't serve Hashem - אין השכינה שורה מתוך עצבות. But when Yaakov realized that Yosef was spiritually alive his depression left allowing the רוח הקודש to return to him. So the brothers weren't able to answer because they felt guilty; they had in a sense chased Hashem away from Yaakov. From this we learn that to be considered alive, one needs to be connected to Hashem through רוח הקודש or Torah. Today we aren't privileged to be living in a time of true רוח הקודש; therefore, it is important to take advantage of our opportunity to study Torah, our Etz Chaim, to be considered alive and vibrant.