Toldot- A Timeline Through Deductive Reasoning

Deductive reasoning: a logical process in which a conclusion drawn from a set of premises contains no more information than the premises taken collectively (ref. dictionary.com)

When trying to problem solve, deductive reasoning helps us logically move from one step to the next. Deductive reasoning allows us to look at the information that we are provided with and state, with certainty, that the next logical step can also be relied on, because the original information proves the next step. Each step that is proven through deductive reasoning can then be relied on as a fact to support our logical thinking towards a final solution to the problem at hand.

As we've been reading through the parsha each week, we have followed storylines which offer some concrete sense of time. However, taken together, how much time is actually passing between each phase of each story? If we take the individual pieces of information that we are provided with from the text and Rashi's commentaries, we can use deductive reasoning to calculate some of the missing pieces of information in order to put together a fuller picture for ourselves. Is the story between the parshiot a straight timeline, or is it broken into parts dealing with each "main character"? With some deduction, we can find out. (My completed storyline for the primary Toldot "characters" with some added information appears at the bottom of this post. Check your calculations and timeline against mine and see how they match-up. Can you fill in the extra information that I calculated?)

Whenever sorting information for problem solving, the first step is to map out the information that you have.

• From Lech Lecha 17;17 and Vayeira 21;2 we know that when Isaac was born, Sarah was 90 years old and Abraham was 100 years old
• From Chayei Sarah 23;1 we know that Sarah lived to be 127 years old
• From Rashi's commentary on Sarah's death, we know that she died upon hearing the news that Isaac was to be sacrificed at the akedah
• From Rashi on Toldot 25;20, we know that Rebecca was born in the year of the akedah
• From Chayei Sarah 25;7, we know that Abraham lived to be 175 years old
• From Toldot 25;20, we know that Isaac was 40 years old when he married Rebecca
• From Toldot 25;26, we know that Isaac was 60 years old when Esau and Jacob were born
• From Rashi's commentary on Toldot 25;27, we know that Jacob bought Esau's birthright when they were 13 years old
• From Rashi's commentary on Toldot 27;2, we know that Jacob took Esau's blessing from Isaac when Isaac was 123 years old
• From Toldot 26;34, we know that Esau was 40 years old when he married Judith and Basemath

The second step to problem solving is to identify the questions that you are trying to answer.
--How old was Isaac at the akedah (and Sarah's death)?
--How old was Isaac at Abraham's death?
--How old was Rebecca when she married Isaac?
--How old was Rebecca when Esau and Jacob were born?
--How old were Isaac and Rebecca when Esau sold his birthright?
--How old were Jacob, Esau, and Rebecca when Isaac gave Jacob Esau's blessing?
--How old were Rebecca and Isaac when Esau was married?
--How old is Jacob (and Esau) at the end of Toldot?

Now let's see what information we can use to answer these questions:
--How old was Isaac at the akedah (and Sarah's death)?

• Sarah was 90 when Isaac was born, and she was 127 when she heard of the akedah. 
• 127-90=37, so Isaac was 37 at the akedah and when Sarah died

--How old was Isaac at Abraham's death?

• Abraham was 100 when Isaac was born, and Abraham lived to be 175.
• 175-100=75, so Isaac was 75 when Abraham died

--How old was Rebecca when she married Isaac?

• Isaac was 37 at the akedah, which was the same year that Rebecca was born.
• Isaac was 40 when he married Rebecca.
• 40-37=3, so Rebecca was 3 when they were married (keeping strictly to math here, no societal norms commentaries)

--How old was Rebecca when Esau and Jacob were born?

• Isaac was 60 when they were born
• Isaac was 37 years older than Rebecca
• 60-37=23, so Rebecca was 23 when they were born

--How old were Isaac and Rebecca when Esau sold his birthright?

• Isaac was 60 when they were born; Rebecca was 23 when they were born
• Esau and Jacob were 13 when the birthright was sold
• 60+13=73, so Isaac was 73; 23+13=36, so Rebecca was 36

--How old were Jacob, Esau, and Rebecca when Isaac gave Jacob Esau's blessing?

• Isaac was 60 when they were born; Rebecca was 23 when they were born
• Isaac was 123 when he gave Jacob Esau's blessing
• 123-60=63, so Jacob and Esau were 63; 23+63=86, so Rebecca was 86

--How old were Rebecca and Isaac when Esau was married?

• Isaac was 60 when they were born; Rebecca was 23 when they were born
• Esau was 40 when he was married
• 60+40=100, so Isaac was 100; 23+40=63, so Rebecca was 63

(click on the picture for a larger view of the timeline)

From this timeline, we can see that, although most of the storylines in these few parshiot are in order, there are some pieces of information that are placed out of order, seemingly to keep them together with the sections that discuss the particular "character" in more depth.